Co-reporter:Wei-Lu Ding, Yi-Ming Cui, Li-Na Yang, Quan-Song Li, Ze-Sheng Li
Dyes and Pigments 2017 Volume 136() pp:450-457
Publication Date(Web):January 2017
DOI:10.1016/j.dyepig.2016.09.002
•A theoretical design of Zn-porphyrin dye in co-sensitizing system.•Different π-spacers are introduced.•Dye 4 can be the potential candidate.•Balanced parameters can achieve the high efficiency.Co-sensitization has been considered as a helpful strategy for improving the conversion efficiency in dye-sensitized solar cells (DSSCs). In this present, Zinc porphyrin dyes 1–4 have been designed based on SM315 which has achieved the record efficiency (13%). Simultaneously, these new dyes are anticipated to replace the previous dye XW11 which is analogous to SM315 in co-sensitization system. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been carried out on the electronic structure and optical properties. Our results show that dye 4 can be the candidate due to its complementary absorption spectrum with co-sensitizer WS-5, sound lifetime of excited state, stronger electronic coupling with TiO2, larger electron injection rate constant, and smaller electron-hole recombination rate constant, as well as most positive-shift of the CB of TiO2. We hope this work is helpful for design Zn-porphyrin dye with target properties to improve the performance of DSSCs.
Co-reporter:Shuai Feng, Quan-Song Li, Thomas A. Niehaus, Ze-Sheng Li
Organic Electronics 2017 Volume 42() pp:234-243
Publication Date(Web):March 2017
DOI:10.1016/j.orgel.2016.12.043
•Effects of donating groups in DSSC are studied by DFT and Marcus theory.•Energy-mismatch of donor and acceptor results in poor dye regeneration.•Stronger intermolecular charge transfer increases dye aggregation.A series of phenothiazine-based dyes containing different auxiliary chromophores (TP, TTP, EP, and EEP) bring about unusual power conversion efficiency (PCE) for the corresponding dye-sensitized solar cells (DSSCs): EEP with the best electron-donating capability provides the lowest PCE of 2.24%, while TP with the weakest electron-donating capability leads to the highest PCE of 8.07%. The underlying influencing factors have been investigated by considering the electronic structures and aggregation properties based on density functional theory and Marcus theory. We found that the energy-mismatch between electron-donating units and the PTZ moiety results in poor EEP dye regeneration. Additionally, molecular dynamics simulations illustrate that the increased intermolecular interaction energy induced by preferable electron-donating groups aggravates the intermolecular aggregation. Especially, the calculated average values of the time-dependent intermolecular lateral charge transfer rate k for (EEP)2 are nearly one order of magnitude higher than those of (TP)2, revealing a more robust π-π stacking interaction induced by the donor unit of EEP. Importantly, the dye-TiO2 interactions have been taken into account, which are absent in many previous theoretical work but crucial for accurate describing the aggregations. These deeper insights into the regeneration process and the aggregation mechanism induced by different donor units encourage researchers to balance various properties in designing novel components for photovoltaic devices.
Co-reporter:Wen-Jie Wu, Quan-Song Li, and Ze-Sheng Li
The Journal of Physical Chemistry A 2017 Volume 121(Issue 4) pp:
Publication Date(Web):January 3, 2017
DOI:10.1021/acs.jpca.6b09495
Understanding the photochemistry of organoboron compounds is essential to expand optoelectronic applications. In this work, the complete active space self-consistent field (CASSCF) and its second-order perturbation (CASPT2) methods combining with density functional theory (DFT) have been employed to investigate the elimination mechanisms of compound 6,7-dihydro-54-benzo[d]pyrido[2,1-f][1,2]azaborininr (B4) on the ground state (S0) and the first excited state (S1). B4 is one of the 1,2-B,N-heterocycles that undergo competitive thermal elimination and photoelimination depending on the substitution groups on the B atom and the chelate backbone, thus providing a high-selectivity synthesis strategy for luminescent compounds. Since the energy barrier from B4 to BH3-pyrido[1,2-a]isoindole (D1) and pyrido[1,2-a]isoindole (A1) on the ground state is lower than that from B4 to 54-benzo[d]pyrido[2,1-f][1,2]azaborininr (C4), the retraction ring reaction is expected to proceed with larger probability than the H2 elimination upon heating. On the contrary, photoelimination of H2 may take place easily due to the almost barrierless pathway on the S1 state. Remarkably, we have located an energetically available conical intersection (S1/S0)X-1, which allows for ultrafast S1 → S0 decay and subsequently generation of C4. Our results not only throw light on the experimental observations of the selectivity of thermal elimination and photoelimination but also provide detailed information on the excited state as instructional implications for further synthesis and application of B,N-embedded aromatics.
Co-reporter:Wei-Lu Ding;Xing-Liang Peng;Zhu-Zhu Sun;Ze-Sheng Li
Nanoscale (2009-Present) 2017 vol. 9(Issue 43) pp:16806-16816
Publication Date(Web):2017/11/09
DOI:10.1039/C7NR04847E
Herein, we have investigated the effect of both the bifunctional linker (L1, L2, L3, and L4) and ZnO morphology (porous nanoparticles (NPs), nanowires (NWs), and nanotubes (NTs-A and NTs-Z)) on the electron injection in CdSe QD sensitized solar cells by first-principles simulation. Via calculating the partitioned interfaces formed by different components (linker/QDs and ZnO/linker), we found that the electronic states of QDs and every ZnO substrate are insensitive to any linker, while the frontier orbitals of L1–L4 (with increased delocalization) manifest a systematical negative-shift. Because of the lowest unoccupied molecular orbital (LUMO) of L1 compared to its counterparts aligned in the region of the virtual states of QDs or the substrate with a high density of states, it always yields a stronger electronic coupling with QDs and varied substrates. After characterization of the complete ZnO/linker/QD system, we found that the electron injection time (τ) vastly depends on both the linker and substrate. On the one hand, L1 bridged QDs and every substrate always achieve the shortest τ compared to their counterpart associated cases. On the other hand, NW supported systems always yield the shortest τ no matter what the linker is. Overall, the NW/L1/QD system achieves the fastest injection by ∼160 fs. This essentially stems from the shortest molecular length of L1 decreasing the distance between QDs and the substrate, subsequently improving the interfacial coupling. Meanwhile, the NW supported cases generate the less sensitive virtual states for both the QDs and NWs, ensuring a less variable interfacial coupling. These facts combined can provide understanding of the effects contributed from the linker and the oxide semiconductor morphology on charge transfer with the aim of choosing an appropriate component with fast directional electron injection.
Co-reporter:Wei-Jie Chi;Dao-Yuan Zheng;Xiao-Fang Chen;Ze-Sheng Li
Journal of Materials Chemistry C 2017 vol. 5(Issue 38) pp:10055-10060
Publication Date(Web):2017/10/05
DOI:10.1039/C7TC03232C
Although perovskite solar cells (PSCs) have recently achieved power conversion efficiencies (PCE) of over 23.6%, one major bottleneck for further improving the PCE is the lack of suitable hole transport materials. To further understand the structure–property relationship of hole transport materials and design new materials, we calculated the energy levels and optical properties of a series of thienothiophene derivatives by using density functional theory, and their hole transfer behaviors were also described by the Marcus charge transfer theory. It is found that the HOMO energies gradually decrease as the number of thiophene rings (n) increases when n is less than 4. However, when n is more than 4, the HOMO energy is a constant value of −5.23 eV. As for the LUMO energy and energy gaps, they show a similar change trend, that is, a gradual decrease with growing n. Optical calculations showed that thienothiophene extension cannot affect the Stokes shifts of thienothiophene derivatives. Importantly, it is found that the hole mobility of thienothiophene molecules is co-determined by the molecular size and odd or even number of thiophthene units, and all investigated thienothiophene molecules show higher hole mobility than Sprio-OMeTAD due to the face-to-face packing model. These results provide useful information to further develop suitable HTMs used in PSCs.
Co-reporter:Yan-Ling Wang;Quan-Song Li;Ze-Sheng Li
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 34) pp:23444-23453
Publication Date(Web):2017/08/30
DOI:10.1039/C7CP04372D
All polymer organic solar cells afford unique potentials due to the tunable chemical and electronic properties of both polymer donors and polymer acceptors. Compared with the rapid development of polymer donors, the development of polymer acceptors lags far behind. To seek high-performance polymer acceptors used in organic solar cells, based on the experimentally reported D–A polymer acceptor (NDI2OD-T2)n (P1), a series of novel acceptors, designated as (BDTNDI2OD-T2)n(P2), (BDTNDTI)n(P3), (BDTNDI2OD-Tz2)n(P4), and (BDTNDTzI)n(P5), were designed by introduction of a benzodithiophene (BDT) unit and the nitrogen atom in the bridged thiophene ring. The density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods were applied to study the effect of the BDT unit and the nitrogen atom on the geometrical, optical, electronic, and charge transport properties. The obtained results show that incorporation of the electron-donating BDT unit into P1 and the replacement of a carbon atom by the nitrogen atom in the bridged thiophene ring are effective strategies to lower the lowest unoccupied molecular orbital (LUMO) energy and exciton binding energy, and enhance light-absorbing capacity and electron mobility. Moreover, among the investigated molecules, P2 and P5 exhibit stronger and broader light absorption, higher light absorption efficiency and exciton separation ability as well as electron mobility; therefore they are recommended as promising polymer acceptors for future high-efficiency organic solar cells.
Co-reporter:Xing-Liang Peng;Wei-Lu Ding;Quan-Song Li;Ze-Sheng Li
Organic Chemistry Frontiers 2017 vol. 4(Issue 6) pp:1153-1161
Publication Date(Web):2017/05/31
DOI:10.1039/C7QO00083A
Upon application of heat or UV light, acyl azides undergo the Curtius rearrangement leading to an isocyanate with the loss of nitrogen gas, which is of great importance in organic chemistry and biological science. The mechanism of the thermal Curtius rearrangement has been made clear, but the photo-induced one remains controversial. In this work, the mechanism of photo-induced Curtius rearrangement of chlorodifluoroacetyl azide F2ClCC(O)N3 has been investigated using the MS-CASPT2//CASSCF method combined with density functional theory (DFT). Our calculations disclosed that illumination with light of 225 nm or 193 nm populates the S2(π1π2*) state or S4(nOπ1*) state of F2ClCC(O)N3 at the Franck–Condon region, followed by internal conversion to the S1 state minimum of (π1π1*) character. The reaction is initiated through the elimination of N2 that leads to a nitrene intermediate in the S1 state. Subsequently, the S1 state nitrene decays to the ground state via an S1/S0 conical intersection, resulting in either nitrene or isocyanate. The obtained results show that F2ClCC(O)N3 prefers to undergo photo-induced Curtius rearrangement in a stepwise mechanism via the nitrene intermediate. This work not only provides a clear mechanism for the Curtius rearrangement of chlorodifluoroacetyl azide, but also gives new insights into the photochemistry of acyl azides and nitrene where conical intersections between excited states and ground states play key roles.
Co-reporter:Wei-Lu Ding;Xing-Liang Peng;Zhu-Zhu Sun;Ze-Sheng Li
Journal of Materials Chemistry A 2017 vol. 5(Issue 27) pp:14319-14330
Publication Date(Web):2017/07/11
DOI:10.1039/C7TA03349D
Herein, we theoretically designed and characterized the bifunctional aromatic linker PDTCA utilized in CdSe quantum dot-sensitized solar cells and further modified its benzene ring by varying both its functional groups (NMe2, NH2, OMe, OH, Me, Cl, F, CN, NO2, and CF3) and sites (P1–P4). Via simulating the divided interface-1 (TiO2/linker) and interface-2 (linker/QDs), we found that the substitutions on the P1 and P2 sites of PDTCA by most of these groups could outperform the substitutions on the P3 and P4 sites. On the one hand, these substitutions positively shifted the edge of the unoccupied states of TiO2 towards the vacuum level, favoring a large open-circuit voltage (Voc). On the other hand, it red-shifted the maximum absorption peak (λmax) towards the low-energy region, lessening the hole delocalization from the linker to the QDs and weakening the electron–hole recombination. Overall, the TiO2/linker/CdSe QDs system belongs to a type-II energy level alignment, and the edges of the occupied and unoccupied states of the QDs were insensitive to the variation both of the groups and sites. After excluding the undesired P3 and P4 sites, the electron injection efficiency (ηinj) in the screened groups containing NH2-, Cl-, CN-, and NO2-based TiO2/linker/CdSe QDs systems were calculated. The result showed that the CN-associated systems yielded almost complete electron injection (ηinj ∼ 99%) regardless of the functional site as compared to the picture before the substitution (57%); however, the NH2-, Cl-, and NO2-containing systems produced a site-dependent ηinj pronouncedly. This was attributed to the overwhelming injection rate constant (kinj) as compared to the recombination rate constant (krec) (1013vs. 1010 s−1) in the CN-capped interfaces, whereas in the Cl-, NH2-, and NO2-related systems, the considerable and even larger krec with regard to kinj suppressed the efficient injection. Finally, the CN(P1)-PDTCA and CN(P2)-PDTCA are screened out as the most desired candidates for future application due to their performances favoring a large Voc, lower recombination, a red-shifted λmax, and their ability to boost electron injection.
Co-reporter:Yuan-Chun Hu, Wei-Lu Ding, Xing-Liang Peng, Ze-Sheng Li
Journal of Molecular Graphics and Modelling 2017 Volume 77(Volume 77) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jmgm.2017.09.005
•A theoretical design of D-A-π-A architecture dyes with extended donor size.•Fluorescence energy transfer improves dye’s light-harvesting.•The two novel dyes possess the capability of anti-aggregation.•Dye 3 performs nicely and can be as the potential candidate.We have theoretically designed two D-A-π-A dyes 3 and 4 based on the efficient references 1 and 2 by introducing an extra electron donor unit (D2). Via calculating the electronic structures of isolated dyes, we obtain that dyes 3 and 4 possess stronger light-harvesting efficiency imparted by the fluorescence energy transfer of D2 part, maintain comparable lifetime of excited states, and shorten the electron injection time significantly with regard to 1 and 2. Meanwhile, dye 3 positively shifts the edge of virtual states of TiO2 in a larger extent compared to its counterparts. Then after considering the alignment morphology of multiple dyes adsorbed on TiO2 surface, we find that dyes 3 and 4 manifest the capability of anti-aggregation obviously, which is evidenced by the smaller quantity of intermolecular electronic coupling compared to that of dyes 1 and 2, definitively illustrating the prominent performance of novel dyes with the bulky D2 moiety. Finally, dye 3 is screened out as the potential candidate for future application.Download high-res image (136KB)Download full-size image
Co-reporter:Ling Liu, Xiuhui Zhang, Zesheng Li, Yunhong Zhang, Maofa Ge
Chemosphere 2017 Volume 186(Volume 186) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.chemosphere.2017.08.007
•Potential hydration processes of glyoxylic acid in the atmosphere were studied.•The effective rate constants including concentrations of catalysts were calculated.•Water and sulfuric acid are effective in catalyzing hydration of glyoxylic acid.•Hydration of glyoxylic acid is potentially fast in coastal and polluted regions.Oxocarboxylic acids are one of the most important organic species found in secondary organic aerosols and can be detected in diverse environments. But the hydration of oxocarboxylic acids in the atmosphere has still not been fully understood. Neglecting the hydration of oxocarboxylic acids in atmospheric models may be one of the most important reasons for the significant discrepancies between field measurements and abundance predictions of atmospheric models for oxocarboxylic acids. In the present paper, glyoxylic acid, as the most abundant oxocarboxylic acids in the atmosphere, has been selected as an example to study whether the hydration process can occur in the atmosphere and what the kinetic process of hydration is. The gas-phase hydration of glyoxylic acid to form the corresponding geminal diol and those catalyzed by atmospheric common substances (water, sulfuric acid and ammonia) have been investigated at the CCSD(T)-F12/cc-pVDZ-F12//M06-2X/6-311++G(3df,3pd) level of theory. The contour map of electron density difference of transition states have been further analyzed. It is indicated that these atmospheric common substances can all catalyze on the hydration to some extent and sulfuric acid is the most effective reducing the Gibbs free energy of activation to 9.48 kcal/mol. The effective rate constants combining the overall rate constants and concentrations of the corresponding catalysts have shown that water and sulfuric acid are both important catalysts and the catalysis of sulfuric acid is the most effective for the gas-phase hydration of glyoxylic acid. This catalyzed processes are potentially effective in coastal regions and polluted regions.
Co-reporter:Wei-Jie Chi, Quan-Song Li and Ze-Sheng Li
Nanoscale 2016 vol. 8(Issue 11) pp:6146-6154
Publication Date(Web):22 Feb 2016
DOI:10.1039/C6NR00235H
Perovskite solar cells (PSCs) with organic small molecules as hole transport materials (HTMs) have attracted considerable attention due to their power conversion efficiencies as high as 20%. In the present work, three new spiro-type hole transport materials with spiro-cores, i.e. Spiro-F1, Spiro-F2 and Spiro-F3, are investigated by using density functional theory combined with the Marcus theory and Einstein relation. Based on the calculated and experimental highest occupied molecular orbital (HOMO) levels of 30 reference molecules, an empirical equation, which can predict the HOMO levels of hole transport materials accurately, is proposed. Moreover, a simplified method, in which the hole transport pathways are simplified to be one-dimensional, is presented and adopted to qualitatively compare the molecular hole mobilities. The calculated results show that the perovskite solar cells with the new hole transport materials can have higher open-circuit voltages due to the lower HOMO levels of Spiro-F1 (−5.31 eV), Spiro-F2 (−5.42 eV) and Spiro-F3 (−5.10 eV) compared with that of Spiro-OMeTAD (−5.09 eV). Furthermore, the hole mobilities of Spiro-F1 (1.75 × 10−2 cm2 V−1 s−1) and Spiro-F3 (7.59 × 10−3 cm2 V−1 s−1) are 3.1 and 1.4 times that of Spiro-OMeTAD (5.65 × 10−3 cm2 V−1 s−1) respectively, due to small reorganization energies and large transfer integrals. Interestingly, the stability properties of Spiro-F1 and Spiro-F2 are shown to be comparable to that of Spiro-OMeTAD, and the dimers of Spiro-F2 and Spiro-F3 possess better stability than that of Spiro-OMeTAD. Taking into consideration the appropriate HOMO level, improved hole mobility and enhanced stability, Spiro-F1 and Spiro-F3 may become the most promising alternatives to Spiro-OMeTAD. The present work offers a new design strategy and reliable calculation methods towards the development of excellent organic small molecules as HTMs for highly efficient and stable PSCs.
Co-reporter:Ping-Ping Sun, Quan-Song Li, Li-Na Yang and Ze-Sheng Li
Nanoscale 2016 vol. 8(Issue 3) pp:1503-1512
Publication Date(Web):03 Dec 2015
DOI:10.1039/C5NR05337D
In recent years, perovskite solar cells have been considerably developed, however the lead in the absorber MAPbI3 is a potential threat to the environment. To explore potential alternatives, the structural and electronic properties of MAGeX3 (X = Cl, Br, I) were investigated using different density functional theory methods, including GGA-PBE, PBE-SOC, HSE06 and HSE-SOC. The results implied that MAGeI3 exhibits an analogous band gap, substantial stability, remarkable optical properties, and significant hole and electron conductive behavior compared with the so far widely used absorber MAPbI3. Moreover, the calculations revealed that the energy splitting resulting from the spin–orbit coupling is evident on Pb, moderate on Ge, I and Br, and negligible on Cl. Our work not only sheds some light on screening novel absorbers for perovskite solar cells but also deepens the understanding of these functional materials.
Co-reporter:Ping-Ping Sun, Quan-Song Li, Shuai Feng and Ze-Sheng Li
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 21) pp:14408-14418
Publication Date(Web):28 Apr 2016
DOI:10.1039/C6CP02105K
Organic–inorganic methylammonium lead halide perovskites have recently attracted great interest emerging as promising photovoltaic materials with a high 20.8% efficiency, but lead pollution is still a problem that may hinder the development and wide spread of MAPbI3 perovskites. To reduce the use of lead, we investigated the structures, electronic and optical properties of mixed MAGexPb(1−x)I3 theoretically by using density functional theory methods at different calculation levels. Results show that the mixed Ge/Pb perovskites exhibit a monotonic decrease evolution in band energy to push the band gap deeper in the near-infrared region and have a red shift optical absorption with an increased proportion of Ge. The results also indicate that lattice distortion and spin–orbit coupling (SOC) strength play important roles in the band gap behavior of MAGexPb(1−x)I3 by affecting the bandwidths of CBM and VBM. The calculations for short circuit current density, open circuit voltage, and theoretical power conversion efficiency suggest that mixed Ge/Pb perovskite solar cells (PSCs) with efficiency over 22% are superior to MAPbI3 and MAGeI3. And notably, MAGe0.75Pb0.25I3 is a promising harmless material for solar cells absorber with the highest theoretical efficiency of 24.24%. These findings are expected to be helpful for further rational design of nontoxic light absorption layer for high-performance PSCs.
Co-reporter:Wei-Lu Ding, Xing-Liang Peng, Ze-Sheng Li
Organic Electronics 2016 Volume 38() pp:384-395
Publication Date(Web):November 2016
DOI:10.1016/j.orgel.2016.09.014
•A theoretical investigation of dyes@TiO2 interfaces in co-sensitizing system.•The role of oligothiophene-functionalized co-sensitizer has been addressed.•Co-sensitizer with increased thiophene suppresses electron-hole recombination.•Total electron injection efficiency depends on the number of oligothiophene.Co-sensitizer has been employed in dye-sensitized solar cells (DSSCs) to enhance light harvesting at organic/inorganic heterogeneous. Here, the multiple dyes@TiO2 interface has been investigated by density functional theory simulations, to explore the role of varied oligothiophene-functionalized co-sensitizers on the electron injection efficiency. In presence of co-sensitizers, the simulated absorption spectra broaden with the increasing of the number of thiophene from 0, 1, to 2. Meanwhile, the co-sensitizer modifies the energy alignment of interface, and influences the electronic coupling between dye and TiO2. Critically, the ratio of electron-hole recombination and electron injection rates krec/kinj based on Marcus theory for both dye and co-sensitizer decrease significantly with increasing of the number of oligothiophene, resulting in the improved electron injection efficiency. Our result implies that the electron injection efficiency depends on the number of thiophene in co-sensitizer largely, and appropriate number plays an active role in tuning the electronic properties of hybrid heterostructure.
Co-reporter:Meng Tian, Wei-Jie Chi, Quan-Song Li and Ze-Sheng Li
RSC Advances 2016 vol. 6(Issue 53) pp:47607-47615
Publication Date(Web):29 Apr 2016
DOI:10.1039/C6RA05352A
In this work, we report on the design and full prediction of four poly-nitro cage compounds, octanitrooctaprismane (ONOP), octanitrooctaazaprismane (ONOAP), tetranitrooctaprismane (TNOP), and tetranitrooctaazaprismane (TNOAP) at the B3LYP/6-31G (d,p) level using density functional theory (DFT). The results show that all compounds possess large positive heats of formation (HOF) and specific enthalpies of combustion (ΔHC). The detonation velocity (D) and pressure (P) are calculated using Kamlet–Jacobs equations, and ONOP, ONOAP, and TNOAP showed a superior performance in comparison to commonly used energetic materials, 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and 1,3,5-trinitro-1,3,5-triazinane (RDX). Calculation of the bond dissociation energy (BDE) is carried out and reveals good thermal stabilities for all compounds. In terms of sensitivity, molecules with four nitro groups (TNOP and TNOAP) display lower sensitivity than those with eight nitro groups (ONOP and ONOAP). Importantly, TNOAP outshines other molecules due to its superior energetic properties, compared to those of HMX, and good sensitivity, less than that of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and comparable to that of RDX, so we recommend TNOAP as a promising HEDM candidate.
Co-reporter:Wei-Jie Chi, Quan-Song Li, Ze-Sheng Li
Synthetic Metals 2016 Volume 211() pp:107-114
Publication Date(Web):January 2016
DOI:10.1016/j.synthmet.2015.11.020
•Extension of the thiophene chain brings a red-shift on the absorption spectrum.•Reorganization energies gradually decrease as the number of thiophene rings increases.•S⋯S distances in stacked dimers are inversely proportional to hole mobility.•H114 and H115 exhibit large hole mobility thus are recommended as potential HTMs.We report the effect of the thiophene chain extension on optical property and hole mobility of a set of 3,4,5-tetra[4,4′-bis(methoxyphenyl)aminophen-4″-yl]-thiophene (H111) derivatives (H112, H113, H114, and H115) by using first-principles calculations combined with Marcus theory. Our results show that extension of the thiophene chain not only brings a red-shift on the absorption spectrum, but also enhances the intensity of the largest absorption. Moreover, with the increase of the thiophene number, the reorganization energy between the neutral and cation states gradually reduces, leading to a continuous decrease in exciton binding energy from H111 to H115. Importantly, we reveal that sulfur (S) atoms play dominant roles in hole transfer, and the corresponding S⋯S distances in stacked dimers are inversely proportional to hole mobility. Compared with H111 and H112, H114 and H115 exhibit evidently large hole mobility thus are recommended as potential hole transport materials for perovskite solar cells.
Co-reporter:Li-Na Yang, Shi-Lu Chen and Ze-Sheng Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 16) pp:8308-8315
Publication Date(Web):13 Mar 2015
DOI:10.1039/C5TA00812C
Inspired by the successful utilization of silicon cores axially coordinated by trihexylsiloxy groups in naphthalo/phthalocyanine dyes, using ullazine-based dye JD21 as the prototype, we designed three novel silicon-core JD analogues in this work. Based on the theoretical analysis on the four dyes and the corresponding dye/(TiO2)38 complexes, the Y2 dye with the dithienosilole (DTS) conjugation unit is recognized as a star molecule for its impressive performance in various aspects, including remarkable light-harvesting capability, large driving force for dye regeneration (ΔGreg = 0.65 eV), excellent balance between the rates of electron injection (kinj = 1.48 × 1012 s−1) and electron–hole recombination (krec = 1.68 × 1010 s−1), and high stability for the adsorbed system Y2/(TiO2)38. It is thus proposed as a promising candidate for application in dye-sensitized solar cells (DSCs).
Co-reporter:Wei-Lu Ding, Quan-Song Li and Ze-Sheng Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 39) pp:19948-19959
Publication Date(Web):24 Aug 2015
DOI:10.1039/C5TA05190H
We have performed a theoretical investigation using a combination of DFT/TDDFT and molecular dynamics simulations to explain the relationship between bulky donor groups and higher efficiencies for a recent indoline sensitizer YA422 derived from its counterparts IQ4 and YA421, which features an extended donor subunit for use in dye-sensitizer solar cells (DSSCs). Firstly, the absorption and fluorescence properties indicate that the Förster resonance energy transfer occurs only in YA422, where the λems of the donor group D2 matches with the λabs of the whole molecule around the band at 533 nm. Secondly, the simulated heterogeneity between the sensitizer and (TiO2)124 before and after the co-adsorption of the additive CDCA shows that the nearest position of every monomer in YA422 is separated by a row of Ti atoms due to the steric hindrance introduced by the extended donor group, which not only forms the ordered alignment but also prevents aggregation. Meanwhile, the separated position decreases the self-decay which is shown by the complete intramolecular charge transfer in the aggregate structure of (TiO2)124. Furthermore, using a combined Newns–Anderson approach and the Marcus equation, a faster electron injection rate kinject of YA422 (2.27 × 1015 s−1) is obtained compared with those of IQ4 and YA421. We confirm that the higher conversion efficiency achieved by YA422 is caused by its bulky donor group which enhances the electron-donation and transfer. Finally, based on the above insights, we designed a novel sensitizer DW1 which is expected to be a promising candidate due to its enhanced absorption and larger kinject compared with those of YA422.
Co-reporter:Zhu-Zhu Sun, Quan-Song Li, Min Zhang, Ze-Sheng Li
Journal of Power Sources 2015 Volume 294() pp:264-271
Publication Date(Web):30 October 2015
DOI:10.1016/j.jpowsour.2015.06.094
•A theoretical study on regeneration of Ru(II)-dyes by Co-mediators.•Regeneration rates go up with the increase degree of dye protonation.•Design of charge-neutral dye is good for the compatibility between Ru(II)-dyes and Co-mediators.•Electronic coupling is greatly influenced by the distribution of frontier orbitals of the reactants.The regeneration of ruthenium(II) dyes by cobalt redox mediator in dye-sensitized solar cells (DSSCs) has been investigated using density functional theory combined with the Marcus theory of electron transfer. Our results show that the regeneration reaction rates gradually increase with the growth of the dye protonation degree. By comparing the natures of protonated and deprotonated states, we reveal that design of charge-neutral dye is the best choice to obtain fast dye regeneration and suppress the undesired recombination reaction of the injected photoelectrons. Furthermore, the dye-cobalt mediator associated configuration is found to influence the regeneration reaction rates remarkably by varying the electronic coupling energy. The electronic coupling energy largely depends on the frontier orbitals distribution of the reactants, so the matching of the electronic configuration of the dyes and the cobalt mediators should be judiciously conceived.
Co-reporter:Wei-Jie Chi and Ze-Sheng Li
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 8) pp:5991-5998
Publication Date(Web):21 Jan 2015
DOI:10.1039/C4CP05096G
The electronic structures, optical properties and hole mobilities of 4-(4-phenyl-4-α-naphthylbutadieny)-triphenylamine and its five derivatives are investigated by density functional theory (DFT). The results show that the highest occupied molecular orbital (HOMO) of all molecules is almost fully delocalized throughout the whole molecule, and the substituents –N(CH3)2 and –C6H5 denoted as molecules 6 and 2, respectively, have the largest contribution to the HOMO, which is favorable for hole transfer integral and hole mobility. Spectrum analysis indicates that all molecules have large Stokes shifts based on absorption and emission spectra. In addition, it is found that the hole reorganization energy of all molecules is about 0.5 times compared to that of electrons, which implies that hole mobility is bigger than electron mobility. On the basis of predicted packing motifs, the hole mobilities (u) of all molecules are also obtained. The largest hole mobility of molecule 2 (0.1063 cm2 V−1 s−1) is found to be higher than that of other molecules due to the face-to-face stacking mode, which suggests that –C6H5 is a good substituent group for improving hole mobility compared to other electron releasing groups. We hope that our results will be helpful for the further rational molecular design and synthesis of novel hole transport materials (HTMs) for high performance perovskite-type solar cells.
Co-reporter:Weijie Chi and Zesheng li
RSC Advances 2015 vol. 5(Issue 10) pp:7766-7772
Publication Date(Web):17 Dec 2014
DOI:10.1039/C4RA12773K
Density functional theory simulations were performed to calculate the heats of formation in the gas state [HOF(g)] and in the solid state [HOF(s)], detonation performance and stability of twelve polydinitroaminoprismanes. Our results show that C2 has the best detonation properties of all the molecules, the detonation velocity is 9.56 km s−1 and the detonation pressure is 41.88 GPa, and detonation properties of C2, C3, D1, D2, and D3 are better than those of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX). The stability of all the molecules was investigated by analyzing the energy gaps, bond dissociation energies, and characteristic heights of the molecules. The results show that the N–NO2 bonds of all the molecules are trigger bonds during the thermolysis initiation process, and seven molecules (A, B1–B3 and C1–C3) are less sensitive than 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0.0]dodecane (CL-20). The results of this study may provide basic information for the further study of this kind of compounds and molecular design of novel energetic materials.
Co-reporter:Hui Zhang, Yan Shang, Hong Zhao, Baozhong Han, Zesheng Li
Computational and Theoretical Chemistry 2015 Volume 1062() pp:99-104
Publication Date(Web):15 June 2015
DOI:10.1016/j.comptc.2015.04.002
•Potential energy surface of valence bond isomerization reaction of acetophenone has been investigated.•The mechanism of voltage stabilizer for increasing electrical breakdown strength of XLPE has been suggested.•Valence bond isomerization reaction of acetophenone can increase electrical breakdown strength as voltage stabilizers.•A fertile theoretical background is provided for preparing the insulation materials of high-voltage cable exceed 500 kV.A theoretical investigation on the mechanisms of acetophenone added to polyethylene as voltage stabilizers is accomplished at the atomic and molecular levels. The five reaction pathways of valence bond isomerization of acetophenone have been elucidated. The electronic structures at the ground states and lowest triplet states of acetophenone and its valence bond isomers were calculated at the B3LYP/6-311+G(d,p) level. The HOMO–LUMO energy gaps, ionization potentials, and electron affinities at the ground states of studied molecules were obtained at the same level. The theoretical results are in good agreement with the available experimental findings. Our calculations indicate that the valence bond isomerization forming the Hückel structure is the major pathway, and the other valence bond isomerizations that yield Dewar, Ladenburg, and Bicyclopropylene acetophenones are minor pathways. Based on these results, several interesting voltage stabilizers have been designed.The addition of acetophenone as voltage stabilizer can increase the alternate current breakdown strength of cross-linking polyethylene (XLPE). Potential energy surface of valence bond isomerization reaction of acetophenone has been investigated. The mechanism of voltage stabilizer for increasing electrical breakdown strength of XLPE has been suggested. It is expected to provide reliable information for preparing the insulation material of high-voltage cable exceed 500 kV.
Co-reporter:Wei-Jie Chi
The Journal of Physical Chemistry C 2015 Volume 119(Issue 16) pp:8584-8590
Publication Date(Web):April 1, 2015
DOI:10.1021/acs.jpcc.5b02401
First principles calculations combined with Marcus theory were carried out to investigate the hole diffusion kinetics of two thiophene-based hole-transporting materials 4,4′,5,5′-tetra[4,4′-bis(methoxyphenyl)aminophen-4″-yl]-2,2′-bithiophene (H112) and 2,2′,5,5′-tetrakis[N,N-di(4-methoxyphenyl)amino]-3,3′-bithiophene (KTM3) in perovskite solar cells (PSCs). The isomers H112 and KTM3 only differ in the almost planar or swivel-cruciform geometry but give rise to significantly different power conversion efficiency (14.7 and 7.3%). We found that the highest occupied molecular orbitals of H112 and KTM3 are on the same energy level, which explains why the two PSCs exhibit similar open-circuit voltage. We showed that the exciton binding energy of H112 is 23.6% smaller than that of KTM3, which indicates an easier generation of free charge carriers in H112. More importantly, the most stable crystal structure of H112 and KTM3, respectively, belongs to P212121 and P21 space groups, where the packing pattern is face-to-face and herringbone model. The face-to-face packing pattern leads to stronger hole couplings between the neighboring H112 molecules and therefore results in substantial hole mobility (6.75 × 10–2 cm2/V s), which is about four hundred times of that in KTM3. This clarifies the obvious enhancement of the short-circuit current density and therefore the overall performance of PSC with H112 as hole-transporting material. Our work has provided new insights into the hole-transporting properties that should be carefully considered for rational design of high-efficiency hole-transporting materials.
Co-reporter:Wei-Jie Chi, Ze-Sheng Li
Comptes Rendus Chimie 2015 18(12) pp: 1270-1276
Publication Date(Web):
DOI:10.1016/j.crci.2015.06.018
Co-reporter:Li-Na Yang;Hong-Yan Zhou;Ping-Ping Sun; Shi-Lu Chen; Ze-Sheng Li
ChemPhysChem 2015 Volume 16( Issue 3) pp:601-606
Publication Date(Web):
DOI:10.1002/cphc.201402745
Abstract
A series of metal-free organic dyes with electron-rich (D) and electron-deficient units (A) as π linkers have been studied theoretically by means of density functional theory (DFT) and time-dependent DFT calculations to explore the effects of π spacers on the optical and electronic properties of triphenylamine dyes. The results show that Dye 1 with a structure of D-A-A-A is superior to the typical C218 dye in various key aspects, including the maximum absorption (λmax=511 nm), the charge-transfer characteristics (D/Δq/t is 5.49 Å/0.818 e−/4.41 Å), the driving force for charge-carrier injection (ΔGinject=1.35 eV)/dye regeneration (ΔGregen=0.27 eV), and the lifetime of the first excited state (τ=3.1 ns). It is thus proposed to be a promising candidate in dye-sensitized solar cell applications.
Co-reporter:Ping-Ping Sun, Quan-Song Li, Li-Na Yang, Zhu-Zhu Sun and Ze-Sheng Li
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 39) pp:21827-21837
Publication Date(Web):26 Aug 2014
DOI:10.1039/C4CP02951H
The structural and electronic properties of an organic dye C258 before and after being adsorbed onto a TiO2(101) surface by two adsorption modes, monodentate (Mha) and bidentate bridging (BBH), have been investigated in detail. The combination of density functional tight-binding (DFTB), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches have been employed. DFT calculations show that C258 has remarkable charge-transfer characteristics, which favors fast electron injection from the excited dye to the conduction band of TiO2. A detailed analysis of the adsorbate contributions of the dye molecule to band states of TiO2 shows a strong coupling of the adsorbate orbitals with the substrate orbitals. Significant electronic transfer characteristics across the interface reveal a direct electron injection mechanism arising from the electronic excitation of the anchoring group of C258 to the conduction bands of TiO2. The adsorption energy and the electron density distribution demonstrate that the BBH structure is more stable and has a stronger coupling with TiO2 than the Mha pattern, which is able to better promote the electron injection to increase the efficiency of dye-sensitized solar cells (DSSCs).
Co-reporter:Zhu-Zhu Sun, Kui-Ming Zheng, Quan-Song Li and Ze-Sheng Li
RSC Advances 2014 vol. 4(Issue 60) pp:31544-31551
Publication Date(Web):15 Jul 2014
DOI:10.1039/C4RA04605F
Density functional theory (DFT) calculations were carried out to explore the effects of chemically modifying the polypyridine ligands and design efficient Co-based redox mediators for dye-sensitized solar cells (DSSCs). Our results showed that the redox properties of cobalt complexes can be well tuned by altering the number and position of nitrogen atoms on the ligand ring. Adding oxygen atoms on the ligand ring will evidently increase the redox potential, which might be unfavorable for the dye regeneration. The designed good redox mediators possess similar redox potential and reorganization energy to the current high-efficiency redox couples, thus are promising to be used in prospective DSSCs.
Co-reporter:Jin-Hua Luo, Quan-Song Li, Li-Na Yang, Zhu-Zhu Sun and Ze-Sheng Li
RSC Advances 2014 vol. 4(Issue 39) pp:20200-20207
Publication Date(Web):24 Apr 2014
DOI:10.1039/C4RA02204A
Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been carried out on the electronic structure and optical properties of a set of heterocycle-fused zinc porphyrazine (ZnPz) derivatives, aiming at screening efficient sensitizers for dye-sensitized solar cells (DSSCs). Our results show that the absorption spectra of the designed dyes shift to longer wavelengths and the light harvesting efficiencies are much higher than isolated ZnPz. Moreover, the designed dyes have larger contributions of the anchoring group to the lowest unoccupied molecular orbitals (LUMOs) compared with the currently best sensitizer YD2-o-C8, indicating enhanced electron injection ability from the sensitizer to the semi-conductor. Furthermore, the designed dyes exhibit good performance in terms of the charge transfer characteristics, the driving force of electron injection and dye regeneration, and the excited-state lifetime. Overall, the designed dyes, especially indigo blue fused ZnPz and acridine fused ZnPz, are revealed to be promising sensitizers for high-efficiency DSSCs.
Co-reporter:Li-Na Yang;Zhu-Zhu Sun; Shi-Lu Chen; Ze-Sheng Li
ChemPhysChem 2014 Volume 15( Issue 3) pp:458-466
Publication Date(Web):
DOI:10.1002/cphc.201300969
Abstract
To design efficient dyes for dye-sensitized solar cells (DSSCs), using a Zn-coordinated phthalocyanine (TT7) as the prototype, a series of phthalocyanine dyes (Pcs) with different metal ions and peripheral/axial groups have been investigated by means of density functional theory (DFT) and time-dependent DFT (TDDFT) methods. Computational results show that the iodinated Al-based dye with a peripheral amino group (Al-I-NH2-Pc) exhibits the largest redshift in the maximum absorbance (λmax). In addition, Al-based dyes have appropriate energy-level arrangements of frontier orbitals to keep excellent balance between electron injection and regeneration of oxidized dyes. Further, it has been found that the intermolecular π-staking interaction in Al-I-Pc molecules is weaker than the other metal-based Pcs, which may effectively reduce dye aggregation on the semi-conductor surface. All these results suggest iodinated Al-based Pcs (Al-I-Pcs) to be potentially promising sensitizers in DSSCs.
Co-reporter:Shi-Lu Chen, Li-Na Yang, Ze-Sheng Li
Journal of Power Sources 2013 Volume 223() pp:86-93
Publication Date(Web):1 February 2013
DOI:10.1016/j.jpowsour.2012.09.053
One of the most significant aspects in the development of dye-sensitized solar cells (DSCs) is the exploration and design of high-efficiency and low-cost dyes. In the present paper, we have reported a theoretical design of potential high-efficiency organic dyes with modified triphenylamine donors, using time-dependent density functional theory with the CAM-B3LYP method. The CAM-B3LYP method is first validated to have very good performance in the descriptions of spectral properties of C214 and C216 dyes. With C214 as a prototype, molecular modifications are then made and a scheme, using NH groups to connect neighboring phenyls in the triphenylamine donor, has been demonstrated to be successful to significantly red-shift the absorption maximum wavelength, extend the lifetime of the first excited state, and decrease the energy gap between HOMO and LUMO. In particular, the change amounts of these properties are illustrated to be dependent on the number of the added nitrogens, a significant finding that may perhaps make it possible to quantificationally regulate properties of organic sensitizers to match diverse requirements in the building of a high-efficiency DSC. The complementary nitrogens have been characterized to be sp2-hybridized and shown to play an important role in assisting in charge transfer.Graphical abstractHighlights► Molecular design of dyes was done by adding NH groups in the triphenylamine donor. ► Developed dyes show significantly red-shifted maximum absorbance and longer lifetime of the first excited state. ► The changes of properties are considerably dependent on the number of the added nitrogens.
Co-reporter:Jin-Hua Luo, Ai-Min Hu, Xiao-Lin Wang, Yun-Hong Zhang, Ze-Sheng Li
Journal of Colloid and Interface Science 2013 Volume 393() pp:340-346
Publication Date(Web):1 March 2013
DOI:10.1016/j.jcis.2012.11.004
Density functional theory (DFT) calculations were applied to investigate the adsorption of water monomer, water clusters on NaNO3(0 0 1) surface. Single water molecule is more likely to locate on the bridge site with its H atom attracted by the O atom of nitrate ion and its O atom adjacent to Na+. Mulliken population analysis shows that fewer electrons transfer from the Na atom of substrate to water molecule. A systematic study of water clusters adsorption at high coverages ranging from 0.5 monolayer (ML), 0.75 ML, 1 ML, 1.25 ML, and 1.5 ML on NaNO3(0 0 1) surface was also investigated, and the results indicate that for 1 ML water adsorption on NaNO3(0 0 1) surface, a water chain is formed among four water molecules through hydrogen bonds. Interestingly, the water molecules are linked through hydrogen bonds to form a 14-membered macrocyclic water ring for 1.5ML adsorption on NaNO3(0 0 1) surface. Our estimated O–H symmetric stretching frequency (νO–H) will have blueshift with decrease of water coverage, which is consistent with the tendency given by experiments.Graphical abstractHighlights► We study the adsorption of water monomer, water clusters on NaNO3(0 0 1) surface. ► Single water molecule is more likely to locate on the bridge site. ► A water chain is formed for 1 ML water adsorption on NaNO3(0 0 1) surface. ► A 14-membered water ring is formed for 1.5 ML adsorption on NaNO3(0 0 1) surface. ► Our estimated νO–H will have blueshift with decreased water coverage.
Co-reporter:Li-Na Yang, Zhu-Zhu Sun, Shi-Lu Chen, Ze-Sheng Li
Dyes and Pigments 2013 Volume 99(Issue 1) pp:29-35
Publication Date(Web):October 2013
DOI:10.1016/j.dyepig.2013.04.015
•Biscarbodithiolic acid-based dyes show the widest absorption spectra and longest lifetimes.•The planarity of π-conjugated segments affects properties of dyes significantly.•Deprotonated dyes show blue-shifted maximum absorbance compared to corresponding protonated dyes.To design a potential high-efficiency dye, the deeper understanding of the nature of anchoring groups is of significance. In the present paper, using density functional theory (DFT) and time-dependent DFT, we have investigated two sets of dyes (CN11s and CN12s) with various anchoring groups, such as biscarbodithiolic acid, sulfonic acid, phosphonic acid, and hydroxamic acid. Our calculations indicate that the biscarbodithiolic acid-based dyes show the best absorption behavior in the visible-light/near-infrared range, i.e. the biggest maximum absorbances (λmax) and the widest absorption spectra. When phosphonic acid is used as the acceptor, dye molecules exhibit the worst absorption properties. Furthermore, the dyes with biscarbodithiolic acid also show the longest lifetime of the first excited state, implying the potentially good ability in electron injection from sensitizer to semi-conductor. The present results reveal that the D-π-A dyes devised with biscarbodithiolic acid may be promising sensitizers for high-efficiency dye-sensitized solar cells.
Co-reporter:Jin-Hua Luo; Yun-Hong Zhang; Ze-Sheng Li
ChemPhysChem 2013 Volume 14( Issue 9) pp:1969-1976
Publication Date(Web):
DOI:10.1002/cphc.201300077
Abstract
The adsorption properties of water molecules on an MgSO4(100) surface were investigated by using density functional theory (DFT) and supercell models. Optimized stable geometries of one and more than one water molecules adsorbed on an ideal MgSO4(100) surface were obtained. The configurations with water molecules adsorbed on atoms of the second and third atomic layers of the MgSO4(100) surface are quite stable. After adsorption, the separations between both the adjacent Mg atoms (RMgMg) and the adjacent O atoms of the surface (ROO) increase, which indicates that the MgSO4(100) surface starts to deliquesce. In addition, water molecules are more likely to adsorb onto a defective surface rather than an ideal surface. Mulliken population analysis suggests that fewer charges transfer to the water molecule from the Mg atom of a defective substrate. Finally, Raman spectra were calculated for 0.5, 1, and 2 ML (ML=monolayer) water adsorbed on an MgSO4(100) surface, which is helpful for further related experiments.
Co-reporter:Yuan Yao;Hui Zhang;Ze-Sheng Li
Journal of Molecular Modeling 2013 Volume 19( Issue 11) pp:4753-4761
Publication Date(Web):2013 November
DOI:10.1007/s00894-013-1975-9
Chalcone isomerase (CHI) catalyzes the intramolecular cyclization of chalcones into flavonoids. The activity of CHI is essential for the biosynthesis of flavonoids precursors of floral pigments and phenylpropanoid plant defense compounds. In the present study, we explored the detailed binding structures and binding free energies for two different active site conformations of CHI with s-cis/s-trans conformers of three chalcone compounds by performing molecular dynamics (MD) simulations and binding free energy calculations. The computational results indicate that s-cis/s-trans conformers of chalcone compounds are orientated in the similar binding position in the active site of CHI and stabilized by the different first hydrogen bond network and the same second hydrogen bond network. The first hydrogen bond network results in much lower binding affinity of s-trans conformer of chalcone compound with CHI than that of s-cis conformer. The conformational change of the active site residue T48 from indirectly interacting with the substrate via the second hydrogen bond network to directly forming the hydrogen bond with the substrates cannot affect the binding mode of both conformers of chalcone compounds, but remarkably improves the binding affinity. These results show that CHI has a strong stereoselectivity. The calculated binding free energies for three chalcone compounds with CHI are consistent with the experimental activity data. In addition, several valuable insights are suggested for future rational design and discovery of high-efficiency mutants of CHI.
Co-reporter:Hui Zhang;Ping Liu;Jing-Yao Liu;Ze-Sheng Li
Journal of Molecular Modeling 2013 Volume 19( Issue 4) pp:1515-1525
Publication Date(Web):2013 April
DOI:10.1007/s00894-012-1704-9
Theoretical investigations were carried out on the multi-channel reactions CF3 + SiHF3, CF3 + SiHCl3, CH3 + SiHF3, and CH3 + SiHCl3. Electronic structures were calculated at the MP2/6-311+G(d,p) level, and energetic information further refined by the MC-QCISD (single-point) method. The rate constants for major reaction channels were calculated by the canonical variational transition state theory with small-curvature tunneling correction over the temperature range of 200–1,500 K. The theoretical rate constants were in good agreement with the available experimental data and were fitted to the three parameter expression: k1a(T) = 2.93 × 10−26T4.25 exp (−318.68/T), and k2a(T) = 3.67 × 10−22T2.72 exp (−1,414.22/T), k3a(T) = 7.00 × 10−24T3.27 exp (−384.04/T), k4a(T) = 6.35 × 10−22T2.59 exp (−603.18/T) (in unit of cm3molecule−1s−1) are given. Our calculations indicate that hydrogen abstraction channel is the major channel due to the smaller barrier height among four channels considered.
Co-reporter:Yuan Yao and Ze-Sheng Li
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 35) pp:7037-7044
Publication Date(Web):04 Jul 2012
DOI:10.1039/C2OB25605C
The reaction pathway of Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase (DHQD) from S. enterica has been studied by performing molecular dynamics (MD) simulations and density functional theory (DFT) calculations and the corresponding potential energy profile has also been identified. On the basis of the results, the catalytic hydrolysis process for the wild-type enzyme consists of three major reaction steps, including nucleophilic attack on the carbon atom involved in the carbon–nitrogen double bond of the Schiff base intermediate by a water molecule, deprotonation of the His143 residue, and dissociation between the product and the Lys170 residue of the enzyme. The remarkable difference between this and the previously proposed reaction mechanism is that the second step here, absent in the previously proposed reaction mechanism, plays an important role in facilitating the reaction through a key proton transfer by the His143 residue, resulting in a lower energy barrier. Comparison with our recently reported results on the Schiff base formation and dehydration processes clearly shows that the Schiff base hydrolysis is rate-determining in the overall reaction catalyzed by type I DHQD, consistent with the experimental prediction, and the calculated energy barrier of ∼16.0 kcal mol−1 is in good agreement with the experimentally derived activation free energy of ∼14.3 kcal mol−1. When the imidazole group of His143 residue is missing, the Schiff base hydrolysis is initiated by a hydroxide ion in the solution, rather than a water molecule, and both the reaction mechanism and the kinetics of Schiff base hydrolysis have been remarkably changed, clearly elucidating the catalytic role of the His143 residue in the reaction. The new mechanistic insights obtained here will be valuable for the rational design of high-activity inhibitors of type I DHQD as non-toxic antimicrobials, anti-fungals, and herbicides.
Co-reporter:Qi Pan, Yuan Yao, Ze-Sheng Li
Computational and Theoretical Chemistry 2012 Volume 1001() pp:60-66
Publication Date(Web):1 December 2012
DOI:10.1016/j.comptc.2012.10.009
Type II dehydroquinate dehydratase (DHQD), catalyzing the dehydration of dehydroquinate to dehydroshikimate, is considered as an attractive target for developing non-toxic antimicrobials, anti-fungals, and herbicides. The enzymes from different sources show distinguishable kinetic isotope effects, suggesting that they probably employ different reaction mechanisms. In the present study, the catalytic mechanism of type II DHQD from Mycobacterium tuberculosis has been reported by performing molecular dynamics simulations and quantum chemical calculations. The results revealed that this enzyme undergoes a two-step E1cB trans-elimination reaction mechanism and the calculated overall energy barrier of ∼17.7 kcal/mol is in excellent agreement with the experimental value. The developed enolate intermediate does not convert to enol intermediate by abstracting a solvent-derived proton and is therefore stabilized by Asn12 residue through strong hydrogen bonding interaction, reasonably explaining the observed kinetic isotope effect. Without the catalytic role of Asn12 residue, the overall energy barrier raises ∼4.5 kcal/mol.Graphical abstractHighlights► The reaction mechanism of the Mycobacterium tuberculosis type II DHQD was studied. ► It undergoes a two-step E1cB trans-elimination with an enolate intermediate. ► This mechanism can reasonably explain the experimental phenomena.
Co-reporter:Jun Ding;Yuan Yao;Hui Zhang
Science Bulletin 2012 Volume 57( Issue 34) pp:4453-4461
Publication Date(Web):2012 December
DOI:10.1007/s11434-012-5280-2
Phosphonylation and aging processes between butyrylcholinesterase with mipafox have been studied at the B3LYP/6-311G(d,p) level of theory. The calculated results indicate that the phosphonylation process employs a two-step addition-elimination mechanism with the addition (the first step) as the rate-limiting step. Two different calculation models revealed that the catalytic triad of butyrylcholinesterase plays an important role in accelerating the reaction. This is the same mechanism as the phosphonylation reaction of acetylcholinesterase by sarin reported by Wang et al. However, the energy barrier of the rate-limiting step in the present reaction is higher than that in phosphonylation reaction of acetylcholinesterase by sarin. This indicates the differences in the phosphonylation activity of sarin and mipafox. The aging process occurs through a two-step addition-elimination mechanism similar to the phosphonylation process with the addition as the rate-limiting step. The solvent effects have been evaluated by using a CPCM model and the results show that the stationary structures and the negative charges around some important atoms involved in the two processes are not significantly different. However, the energy barrier of the phosphonylation process is remarkably decreased, revealing that this process is feasible in solution.
Co-reporter:Hui Zhang;Yuan Yao;XiaoLi Qi
Science China Chemistry 2012 Volume 55( Issue 12) pp:2580-2586
Publication Date(Web):2012 December
DOI:10.1007/s11426-012-4749-9
In this work, we developed the CHARMM all-atom force field parameters for the nonstandard biological residue chalcone, followed by the standard protocol for the CHARMM27 force field development. Target data were generated via ab initio calculations at the MP2/6-31G* and HF/6-31G* levels. The reference data included interaction energies between water and the model compound F (a fragment of chalcone). Bond, angle, and torsion parameters were derived from the ab initio calculations and renormalized to maintain compatibility with the existing CHARMM27 parameters of standard residues. The optimized CHARMM parameters perform well in reproducing the target data. We expect that the extension of the CHARMM27 force field parameters for chalcone will facilitate the molecular simulation studies of the reaction mechanism of intramolecular cyclization of chalcone catalyzed by chalcone isomerase.
Co-reporter:Yuan Yao, Ze-Sheng Li
Chemical Physics Letters 2012 s 519–520() pp: 100-104
Publication Date(Web):
DOI:10.1016/j.cplett.2011.11.019
Co-reporter:Jing-Jing Yu, Yun-Hong Zhang, and Ze-Sheng Li
The Journal of Physical Chemistry B 2012 Volume 116(Issue 41) pp:12597-12604
Publication Date(Web):September 28, 2012
DOI:10.1021/jp307534h
The hydrated bisulfate ion clusters (HSO4–(H2O)n, n = 1–10) were optimized at the M06/6-311++G(d,p) level. The factors affecting ν2-SOH of the clusters involved vibration coupling between ν2-SOH and the water wagging libration mode (W-H2O) and hydrogen bonding effect. In order to understand the vibration coupling between W-H2O and ν2-SOH for the bisulfate clusters, D2O instead of H2O and Se instead of S were used to estimate the uncoupling frequency of ν2-SOH and W-H2O, respectively. For HSO4–·H2O-I, the uncoupling frequencies of ν2-SOH and W-H2O were obtained at 752.0 and 753.4 cm–1. After coupling, the frequencies appeared at 782.2 and 732.6 cm–1. H2S and NH4+ instead of D2O in HSO4–·D2O-II were compared to analyze the effect of hydrogen bond. The sequence of hydrogen bond strength was found to be HSO4–·H2S-II < HSO4–·D2O-II < HSO4–·NH4+-II with the respective ν2-SOH at 736.7, 740.5, and 802.2 cm–1 increasing in the same order. In HSO4–·(H2O)n, coupling appeared when n was from 1 to 8. For HSO4–·(D2O)n, no coupling between ν2-SOH and D2O librations made it possible to understand the hydrogen bonding effect on the ν2-SOH. The frequencies of ν2-SOH for clusters HSO4–(D2O)n almost linearly decreased from 752.0 to 854.6 cm–1 with n from 1 to 10.
Co-reporter:Ping-Ping Sun, Wei-Jie Chi and Ze-Sheng Li
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 35) pp:NaN24536-24536
Publication Date(Web):2016/08/01
DOI:10.1039/C6CP04344E
The stability of perovskite in humid environments is one of the biggest obstacles for its potential applications in light harvesting and electroluminescent displays. Understanding the detailed degradation mechanism of MAGeI3 in moisture is a critical way to explore the practicability of MAGeI3 perovskite. In this study, we report a quantitative and systematic investigation of MAGeI3 degradation processes by exploring the effects of H2O molecules on the structural and electronic properties of the most stable MAGeI3(101) surface under various simulated environmental conditions with different water coverage based on first-principles calculations. The results show that H2O molecules can easily diffuse into the inner side of the perovskite and gradually corrode the structure as the number of H2O molecules increases. As a result of the interactions between perovskite and H2O molecules, a hydrated intermediate will be generated as the first step in the degradation mechanism; the perovskite will further decompose to HI and GeI2. In terms of one MAGeI3 molecule, it will be dissociated completely to GeI2 as a result of hydrolysis reactions with a minimum of 4H2O molecules. In addition, the degradation of the perovskite will also affect the electronic structure, causing a decrease in optical absorption across the visible region of the spectrum and a distinct deformation change in the crystal structure of the material. These findings further illustrate the degradation of the hydrolysis process of MAGeI3 perovskite in humid environments, which should be helpful to inspire experimentalists to take action to prolong the lifetimes of perovskite solar cells to achieve high conversion efficiency in their applications.
Co-reporter:Wei-Lu Ding, Xing-Liang Peng, Zhu-Zhu Sun and Ze-Sheng Li
Journal of Materials Chemistry A 2017 - vol. 5(Issue 27) pp:NaN14330-14330
Publication Date(Web):2017/06/12
DOI:10.1039/C7TA03349D
Herein, we theoretically designed and characterized the bifunctional aromatic linker PDTCA utilized in CdSe quantum dot-sensitized solar cells and further modified its benzene ring by varying both its functional groups (NMe2, NH2, OMe, OH, Me, Cl, F, CN, NO2, and CF3) and sites (P1–P4). Via simulating the divided interface-1 (TiO2/linker) and interface-2 (linker/QDs), we found that the substitutions on the P1 and P2 sites of PDTCA by most of these groups could outperform the substitutions on the P3 and P4 sites. On the one hand, these substitutions positively shifted the edge of the unoccupied states of TiO2 towards the vacuum level, favoring a large open-circuit voltage (Voc). On the other hand, it red-shifted the maximum absorption peak (λmax) towards the low-energy region, lessening the hole delocalization from the linker to the QDs and weakening the electron–hole recombination. Overall, the TiO2/linker/CdSe QDs system belongs to a type-II energy level alignment, and the edges of the occupied and unoccupied states of the QDs were insensitive to the variation both of the groups and sites. After excluding the undesired P3 and P4 sites, the electron injection efficiency (ηinj) in the screened groups containing NH2-, Cl-, CN-, and NO2-based TiO2/linker/CdSe QDs systems were calculated. The result showed that the CN-associated systems yielded almost complete electron injection (ηinj ∼ 99%) regardless of the functional site as compared to the picture before the substitution (57%); however, the NH2-, Cl-, and NO2-containing systems produced a site-dependent ηinj pronouncedly. This was attributed to the overwhelming injection rate constant (kinj) as compared to the recombination rate constant (krec) (1013vs. 1010 s−1) in the CN-capped interfaces, whereas in the Cl-, NH2-, and NO2-related systems, the considerable and even larger krec with regard to kinj suppressed the efficient injection. Finally, the CN(P1)-PDTCA and CN(P2)-PDTCA are screened out as the most desired candidates for future application due to their performances favoring a large Voc, lower recombination, a red-shifted λmax, and their ability to boost electron injection.
Co-reporter:Wei-Jie Chi and Ze-Sheng Li
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 8) pp:NaN5998-5998
Publication Date(Web):2015/01/21
DOI:10.1039/C4CP05096G
The electronic structures, optical properties and hole mobilities of 4-(4-phenyl-4-α-naphthylbutadieny)-triphenylamine and its five derivatives are investigated by density functional theory (DFT). The results show that the highest occupied molecular orbital (HOMO) of all molecules is almost fully delocalized throughout the whole molecule, and the substituents –N(CH3)2 and –C6H5 denoted as molecules 6 and 2, respectively, have the largest contribution to the HOMO, which is favorable for hole transfer integral and hole mobility. Spectrum analysis indicates that all molecules have large Stokes shifts based on absorption and emission spectra. In addition, it is found that the hole reorganization energy of all molecules is about 0.5 times compared to that of electrons, which implies that hole mobility is bigger than electron mobility. On the basis of predicted packing motifs, the hole mobilities (u) of all molecules are also obtained. The largest hole mobility of molecule 2 (0.1063 cm2 V−1 s−1) is found to be higher than that of other molecules due to the face-to-face stacking mode, which suggests that –C6H5 is a good substituent group for improving hole mobility compared to other electron releasing groups. We hope that our results will be helpful for the further rational molecular design and synthesis of novel hole transport materials (HTMs) for high performance perovskite-type solar cells.
Co-reporter:Wei-Jie Chi, Ping-Ping Sun and Ze-Sheng Li
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 39) pp:NaN27077-27077
Publication Date(Web):2016/07/07
DOI:10.1039/C6CP03316D
Methoxyaniline-based organic small molecules with three-dimensional structure have been proven as the most promising hole conductor for state-of-the-art perovskite devices. A fundamental understanding of the electronic properties and hole transport behavior of spiro-CPDT analogues, which is dependent on the number and position of the –OCH3 groups, is significant for their potential applications as hole transport materials of perovskite solar cells. Our results from density functional theory calculations indicate that meta-substitution is more beneficial to reduce the highest occupied molecular orbital (HOMO) levels of molecules compared with ortho- and para-substitution. Furthermore, the hole mobility can be improved by ortho-substitution or mixed ortho- and para-substitution. Most interestingly, it is found that the improvement in hole mobility is at the expense of raising the HOMO level of spiro-CPDT analogues. These results can be useful in the process of designing and synthesizing excellent hole transport materials with suitable HOMO levels and high hole mobility.
Co-reporter:Xing-Liang Peng, Wei-Lu Ding, Quan-Song Li and Ze-Sheng Li
Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 6) pp:NaN1161-1161
Publication Date(Web):2017/03/06
DOI:10.1039/C7QO00083A
Upon application of heat or UV light, acyl azides undergo the Curtius rearrangement leading to an isocyanate with the loss of nitrogen gas, which is of great importance in organic chemistry and biological science. The mechanism of the thermal Curtius rearrangement has been made clear, but the photo-induced one remains controversial. In this work, the mechanism of photo-induced Curtius rearrangement of chlorodifluoroacetyl azide F2ClCC(O)N3 has been investigated using the MS-CASPT2//CASSCF method combined with density functional theory (DFT). Our calculations disclosed that illumination with light of 225 nm or 193 nm populates the S2(π1π2*) state or S4(nOπ1*) state of F2ClCC(O)N3 at the Franck–Condon region, followed by internal conversion to the S1 state minimum of (π1π1*) character. The reaction is initiated through the elimination of N2 that leads to a nitrene intermediate in the S1 state. Subsequently, the S1 state nitrene decays to the ground state via an S1/S0 conical intersection, resulting in either nitrene or isocyanate. The obtained results show that F2ClCC(O)N3 prefers to undergo photo-induced Curtius rearrangement in a stepwise mechanism via the nitrene intermediate. This work not only provides a clear mechanism for the Curtius rearrangement of chlorodifluoroacetyl azide, but also gives new insights into the photochemistry of acyl azides and nitrene where conical intersections between excited states and ground states play key roles.
Co-reporter:Wei-Lu Ding, Quan-Song Li and Ze-Sheng Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 39) pp:NaN19959-19959
Publication Date(Web):2015/08/24
DOI:10.1039/C5TA05190H
We have performed a theoretical investigation using a combination of DFT/TDDFT and molecular dynamics simulations to explain the relationship between bulky donor groups and higher efficiencies for a recent indoline sensitizer YA422 derived from its counterparts IQ4 and YA421, which features an extended donor subunit for use in dye-sensitizer solar cells (DSSCs). Firstly, the absorption and fluorescence properties indicate that the Förster resonance energy transfer occurs only in YA422, where the λems of the donor group D2 matches with the λabs of the whole molecule around the band at 533 nm. Secondly, the simulated heterogeneity between the sensitizer and (TiO2)124 before and after the co-adsorption of the additive CDCA shows that the nearest position of every monomer in YA422 is separated by a row of Ti atoms due to the steric hindrance introduced by the extended donor group, which not only forms the ordered alignment but also prevents aggregation. Meanwhile, the separated position decreases the self-decay which is shown by the complete intramolecular charge transfer in the aggregate structure of (TiO2)124. Furthermore, using a combined Newns–Anderson approach and the Marcus equation, a faster electron injection rate kinject of YA422 (2.27 × 1015 s−1) is obtained compared with those of IQ4 and YA421. We confirm that the higher conversion efficiency achieved by YA422 is caused by its bulky donor group which enhances the electron-donation and transfer. Finally, based on the above insights, we designed a novel sensitizer DW1 which is expected to be a promising candidate due to its enhanced absorption and larger kinject compared with those of YA422.
Co-reporter:Li-Na Yang, Shi-Lu Chen and Ze-Sheng Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 16) pp:NaN8315-8315
Publication Date(Web):2015/03/13
DOI:10.1039/C5TA00812C
Inspired by the successful utilization of silicon cores axially coordinated by trihexylsiloxy groups in naphthalo/phthalocyanine dyes, using ullazine-based dye JD21 as the prototype, we designed three novel silicon-core JD analogues in this work. Based on the theoretical analysis on the four dyes and the corresponding dye/(TiO2)38 complexes, the Y2 dye with the dithienosilole (DTS) conjugation unit is recognized as a star molecule for its impressive performance in various aspects, including remarkable light-harvesting capability, large driving force for dye regeneration (ΔGreg = 0.65 eV), excellent balance between the rates of electron injection (kinj = 1.48 × 1012 s−1) and electron–hole recombination (krec = 1.68 × 1010 s−1), and high stability for the adsorbed system Y2/(TiO2)38. It is thus proposed as a promising candidate for application in dye-sensitized solar cells (DSCs).
Co-reporter:Ping-Ping Sun, Quan-Song Li, Shuai Feng and Ze-Sheng Li
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 21) pp:NaN14418-14418
Publication Date(Web):2016/04/28
DOI:10.1039/C6CP02105K
Organic–inorganic methylammonium lead halide perovskites have recently attracted great interest emerging as promising photovoltaic materials with a high 20.8% efficiency, but lead pollution is still a problem that may hinder the development and wide spread of MAPbI3 perovskites. To reduce the use of lead, we investigated the structures, electronic and optical properties of mixed MAGexPb(1−x)I3 theoretically by using density functional theory methods at different calculation levels. Results show that the mixed Ge/Pb perovskites exhibit a monotonic decrease evolution in band energy to push the band gap deeper in the near-infrared region and have a red shift optical absorption with an increased proportion of Ge. The results also indicate that lattice distortion and spin–orbit coupling (SOC) strength play important roles in the band gap behavior of MAGexPb(1−x)I3 by affecting the bandwidths of CBM and VBM. The calculations for short circuit current density, open circuit voltage, and theoretical power conversion efficiency suggest that mixed Ge/Pb perovskite solar cells (PSCs) with efficiency over 22% are superior to MAPbI3 and MAGeI3. And notably, MAGe0.75Pb0.25I3 is a promising harmless material for solar cells absorber with the highest theoretical efficiency of 24.24%. These findings are expected to be helpful for further rational design of nontoxic light absorption layer for high-performance PSCs.
Co-reporter:Yuan Yao and Ze-Sheng Li
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 35) pp:NaN7044-7044
Publication Date(Web):2012/07/04
DOI:10.1039/C2OB25605C
The reaction pathway of Schiff base hydrolysis catalyzed by type I dehydroquinate dehydratase (DHQD) from S. enterica has been studied by performing molecular dynamics (MD) simulations and density functional theory (DFT) calculations and the corresponding potential energy profile has also been identified. On the basis of the results, the catalytic hydrolysis process for the wild-type enzyme consists of three major reaction steps, including nucleophilic attack on the carbon atom involved in the carbon–nitrogen double bond of the Schiff base intermediate by a water molecule, deprotonation of the His143 residue, and dissociation between the product and the Lys170 residue of the enzyme. The remarkable difference between this and the previously proposed reaction mechanism is that the second step here, absent in the previously proposed reaction mechanism, plays an important role in facilitating the reaction through a key proton transfer by the His143 residue, resulting in a lower energy barrier. Comparison with our recently reported results on the Schiff base formation and dehydration processes clearly shows that the Schiff base hydrolysis is rate-determining in the overall reaction catalyzed by type I DHQD, consistent with the experimental prediction, and the calculated energy barrier of ∼16.0 kcal mol−1 is in good agreement with the experimentally derived activation free energy of ∼14.3 kcal mol−1. When the imidazole group of His143 residue is missing, the Schiff base hydrolysis is initiated by a hydroxide ion in the solution, rather than a water molecule, and both the reaction mechanism and the kinetics of Schiff base hydrolysis have been remarkably changed, clearly elucidating the catalytic role of the His143 residue in the reaction. The new mechanistic insights obtained here will be valuable for the rational design of high-activity inhibitors of type I DHQD as non-toxic antimicrobials, anti-fungals, and herbicides.
Co-reporter:Ping-Ping Sun, Quan-Song Li, Li-Na Yang, Zhu-Zhu Sun and Ze-Sheng Li
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 39) pp:NaN21837-21837
Publication Date(Web):2014/08/26
DOI:10.1039/C4CP02951H
The structural and electronic properties of an organic dye C258 before and after being adsorbed onto a TiO2(101) surface by two adsorption modes, monodentate (Mha) and bidentate bridging (BBH), have been investigated in detail. The combination of density functional tight-binding (DFTB), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches have been employed. DFT calculations show that C258 has remarkable charge-transfer characteristics, which favors fast electron injection from the excited dye to the conduction band of TiO2. A detailed analysis of the adsorbate contributions of the dye molecule to band states of TiO2 shows a strong coupling of the adsorbate orbitals with the substrate orbitals. Significant electronic transfer characteristics across the interface reveal a direct electron injection mechanism arising from the electronic excitation of the anchoring group of C258 to the conduction bands of TiO2. The adsorption energy and the electron density distribution demonstrate that the BBH structure is more stable and has a stronger coupling with TiO2 than the Mha pattern, which is able to better promote the electron injection to increase the efficiency of dye-sensitized solar cells (DSSCs).
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