The development of simple and water-/alcohol-soluble interfacial materials is crucial for the cost-effective fabrication process of polymer solar cells (PSCs). Herein, highly efficient PSCs are reported employing water-/alcohol-soluble and low-cost rhodamines as cathode interfacial layers (CILs). The results reveal that rhodamine-based CILs can reduce the work function of the Al cathode and simultaneously increase the open-circuit voltage, current density, fill factor, and power conversion efficiency (PCE) of PSCs. The solution-processed rhodamine-based PSCs demonstrated a remarkable PCE of 10.39%, which is one of the best efficiencies reported for thieno[3,4-b]thiophene/benzodithiophene:[6,6]-phenyl C71-butyric acid methyl ester-based PSCs so far. The efficiency is also 42.3% higher than that of the vacuum-deposited Ca-based device (PCE of 7.30%) and 21.5% higher than that of the complicated solution-processable polymeric electrolyte poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]-based device (PCE of 8.55%). Notably, rhodamines are very economical and have been extensively used as dyes in industries. Our work indicates that rhodamines have shown a strong potential as CILs compared to their counterparts in the large-area fabrication process of PSCs.Keywords: cathode interfacial layers; conjugated zwitterions; polymer solar cells; rhodamines; solution processing;

•Easily synthesized CHOC60 and CHAC60 were introduced.•Keto and ester group have different effect on photovoltaic performances.•CHOC60 shows comparable photovoltaic performances to PC61BM with low consumption.•P3HT/CHAC60-based devices showed the highest PCE up to 3.15%.The cyclohexanone-containing fullerene mono-adduct, abbreviated as CHOC60, was efficiently prepared through single-step Diels-Alder reaction with 2-(trimethylsilyloxy)-l,3-butadiene and fullerenes. After reduction and esterification, CHOC60 was further converted into cyclohexyl acetate functional fullerene mono-adduct, named as CHAC60, which showed excellent solubility in common organic solvents. P3HT-based bulk heterojunction organic solar cells (OSCs) were fabricated through a typical structure of ITO/PEDOT:PSS/P3HT:(CHOC60 or CHAC60)/Ca/Al. The composite ratios of P3HT and the fullerene derivatives were modified such as 1:0.5, 1:1 and 1:1.5 (w/w). The devices fabricated using CHOC60 or CHAC60 as acceptors achieved the power conversion efficiencies (PCEs) of 2.97% and 3.15%, respectively, which exhibited comparative photovoltaic performances with commercial PC61BM. Moreover, CHOC60-based devices significantly reduced the manufacturing cost by the simplified synthesis of CHOC60 with high yield and low fullerene consumption. The non-aromatic side chain radical CHOC60 and CHAC60 provide a new idea for the design of fullerene derivative acceptors.

As a promising option out of all of the well-recognized candidates that have been developed to solve the coming energy crisis, polymer solar cells (PSCs) are a kind of competitive clean energy source. However, as a convenient and efficient method to improve the efficiency of PSCs, the inherent mechanism of the interfacial modification was still not so clear, and interfacial materials constructed with new units were limited to a large degree. Here we present a new kind of interfacial material consisting of AIE units for the first time, with an efficiency of 8.94% being achieved by inserting TPE-2 as a cathode interlayer. This is a relatively high PCE for PC71BM:PTB7-based conventional PSCs with a single-junction structure. Different measurements, including TEM, AFM, SEM, GIXRD, UPS, SKPM, and SCLC, were conducted to investigate the properties in detail. All of the obtained experimental results confirmed the advantages of the utilization of new interfacial materials with AIE characteristics in polymer solar cells, thus providing an additional choice to develop new organic cathode interfacial layers with high performances.

Highly efficient organic light-emitting diodes (OLEDs) with simplified device structures are widely desired for both scientific research and industrial applications. However, a very limited number of simplified OLEDs have been reported to date. In this work, two multifunctional blueish green emitters, BPTPETPAI and 2TPETPAI, are designed and synthesized. Owing to the presence of a tetraphenylethene (TPE) moiety, their aggregation induced emission (AIE) properties are also investigated. High photoluminescence efficiencies of the two compounds in non-doped films render them good emitters for non-doped devices. Multilayer non-doped devices based on these emitters achieve maximum external quantum efficiencies (EQEs) and current efficiencies (CEs) of 3.13% and 6.14 cd A−1 as well as 3.25% and 6.70 cd A−1 for BPTPETPAI and 2TPETPAI, respectively. Given their shallow highest occupied molecular orbital (HOMO) energy levels, both emitters can also be used as hole injection and hole transporting materials. Based on this, single layer devices show even higher efficiencies with extremely low efficiency roll-off, achieving maximum CEs as high as 7.12 cd A−1 and 7.80 cd A−1 using BPTPETPAI and 2TPETPAI, respectively. These results demonstrate a bright prospect for the development of highly desired multifunctional emitters as well as simplified OLEDs with significant reduction in the fabrication cost of the device.

A series of novel benzophenone-based small molecular cathode interfacial materials with different polar groups including hydroxyl groups, neutral amino groups, amino N-oxide, and sulfobetaine ions were synthesized for PTB7:PC71BM-based polymer solar cells between the active layer and Al electrode. The photovoltaic properties of the devices with these interfacial materials were studied. The differences in interface modification performance of hydroxyl and amino interfacial materials were investigated for the first time. The devices with a solution-processed amino N-oxide-based interlayer showed a PCE of 9.34% with the highest short-circuit current density and fill factor by reducing the series resistance and charge recombination compared to the devices with the other interlayers in this work. The study of structure–property relationships proposes the significant guidance for the design of efficient cathode interface materials in organic solar cells.

•We have designed and synthesized two kinds of solution-processable Substituted Diindenopyrazinediones with improved carrier transport.•Solution-processed device shows PEmax and CEmax of 2.20 l m W−1 and 2.49 cd A−1.•By fine-tuning their carries transfer and injection barriers, DTPADIPY-TCz shows a relatively low efficiency roll-off.Much effort has been devoted to design and synthesize this solution-processable OLEDs, Some significant advances have been achieved with the power efficiencies. However, most of them still lag behind those of evaporated non-doping OLEDs. Two novel peripheral Polyalkyl-carbazole substituted Diindeno-pyrazinediones have been developed for highly-efficient and solution-processable OLEDs. Provide high efficient materials for the solution-processed to reduce costs of OLEDs. By fine-tuning their carriers transfer and injection barriers, solution-processed device based on DTPADIPY-TCz shows highly efficient bluish green emission with a maximum power efficiency (PE) of 6.88 lm W−1, which is among the highest reported to date for solution-processable fluorescent OLEDs with a relatively low efficiency roll-off.Download high-res image (253KB)Download full-size image

Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.

•Novel emissive molecules containing phenanthroimidazole, triphenylamine, carbazole and pyrene units are developed.•Deep blue emission is exhibited by these fluorescent materials.•High thermal stability of materials and low operating voltage of device are observed.•Non-doped OLEDs are constructed with high efficiency and low roll-off.Two phenanthroimidazole derivatives containing triphenylamine, carbazole and pyrene units were designed and synthesized. Highly efficient non-doped deep blue organic light emitting diodes (OLEDs) were fabricated by using these materials as emissive layer. The non-doped devices demonstrated high efficiency (4.24 cd/A, 3.67 lm/W, 4.66%), low efficiency roll-off at higher current densities, and stable deep blue emissions with CIEy around 0.10, which are excellent results for deep-blue OLED devices. This study reveals that the combination of phenanthroimidazole and donor-linker-acceptor strategy has a great potential for developing high performance deep-blue OLEDs.

A novel non-conjugated small-molecule electrolyte was invented as a cathode interlayer in PTB7:PC71BM-based polymer solar cells (PSCs). We discovered a significant synergy effect for improving the device efficiency between methanol treatment and the interlayer. The methanol treatment mainly contributed to the open-circuit voltage, while the interlayer primarily enhanced the short-circuit current and fill factor. Under the effective synergy effect, power conversion efficiencies (PCEs) of PTB7:PC71BM-based PSCs were largely improved from 3.89% to 9.79% for conventional PSCs and from 7.34% to 9.10% for inverted PSCs. Our findings create a new path of interfacial modification for highly efficient PSCs.

•Two novel solution-processable blue fluorescent compounds were synthesized and characterized.•Both of them showed obvious HLCT characteristics.•The maximal efficiencies of p-DTPABI-Cz were up to 3.71 cd/A, 2.33 lm/W, and 2.88%.Two novel dual emitting core hybridized local and charge-transfer emitters of 4′,4‴-(1,1′-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(4,1-phenylene))bis(1H-p-henanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) and 4′,4‴-(1,1′-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(3,1-phenylene))bis(1H-phenanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) were designed and synthesized by introducing two hybridized local and charge-transfer units for single-layer, solution-processable, and blue organic light-emitting diodes (OLEDs). Their absorption, photoluminescence, hybridized local and charge-transfer characteristics, thermal stability and electrochemistry were systematically studied. The single-layered devices by using them as emitters showed efficient blue emission with a maximum brightness 5521 cd/m2 for 4′,4‴-(1,1′-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(4,1-phenylene))bis(1H-p-henanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) and 4403 cd/m2 for 4′,4‴-(1,1′-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(3,1-phenylene))bis(1H-phenanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine). The maximal efficiencies of the former were up to 3.71 cd/A, 2.33 lm/W, and 2.88%. Furthermore, at the high luminescence, the device still indicated good performance with relative low efficiency roll-off. The relationships of structures and properties were also discussed. Most importantly, we provided a new method to construct solution processable small molecules for highly efficient single-layer OLEDs.

We synthesized a new class of polyimides containing a siloxane unit in the main chain and showing an intense photoluminescence (PL) in the ultraviolet (UV) region at room temperature. The PL emission of the sample in solution was observed at around 313 nm with excitation at 266 nm. The fluorescence quantum yield was estimated to be 0.35. The polyimide in the film state also exhibited a strong PL emission around 328 nm. These results indicate that the synthesized polyimide has potential for UV light-emitting applications.

Three 3,4-dithienyl-substituted polythiophene derivatives have been synthesized and characterized. Polymer P2 exhibits the widest light absorption spectrum of the polymers in its polymer chain, which has an alternative donor-acceptor structure. Copolymers blended with 6,6-phenyl-C71-butyric acid methyl ester(PC71BM) as active layers are used to fabricate polymer solar cells (PSCs), and a variety of post-treatments are employed to optimize the PSCs performance. A maximum power conversion efficiency (PCE) of 1.22% is achieved for the conventional configuration device based on P2, and the inverted configuration device of P2 is also prepared for comparison. The results show that the inverted P2 device exhibits a better PCE (1.47%) than that of the conventional device due to the TiO2 nanoparticles and the close energy alignment between the work function of the MoO3 and the HOMO energy levels, which facilitate a light absorption increase and improved charge transport.

A blue fluorophore of N,N-diphenyl-4′′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-amine (BBPI) was utilized as the blue fluorescent emitter and the host of a phosphorescent emitter to fabricate highly efficient fluorescent/phosphorescent (F/P) hybrid white organic light-emitting diodes (WOLEDs) in a single- or multi-emission-layer architecture. For the single-emission-layer WOLEDs consisting of only the blue emitter BBPI and yellow complementary phosphorescent emitter PO-01 in the emission layer, a maximal current efficiency (CE) of 49.1 cd A−1, power efficiency (PE) of 52.0 lm W−1, and external quantum efficiency (EQE) of 16.3% were achieved by modulating the dopant concentration, indicating efficient singlet and triplet exciton separation and utilization ability in the emission layer. An improved EQE of 17.1%, broader spectral coverage, and higher color rendering index (CRI) were achieved by inserting a non-doped blue emission layer of BBPI and a green emission layer of CBP:Ir(PPy)3. A further improved EQE of up to 19.7% could be achieved when an orange-red phosphorescent emitter PQ2Ir was used instead of PO-01, and it is one of the best reported values for the F/P hybrid WOLEDs.

Two blue fluorophores with excellent hybridized local and charge-transfer (HLCT) and “hot exciton” properties were developed as the blue emitter and the host for orange-red phosphor to achieve highly efficient fluorescent/phosphorescent (F/P) hybrid white organic light-emitting diodes (WOLEDs) in a single-emissive-layer single-dopant (SEML-SD) architecture even at a high concentration of phosphorescent dopant. In the devices, part of the triplet excitons of the blue fluorophores can be utilized to realize reverse intersystem crossing from the triplet excited states to the singlet excited states for blue emission, and the diffusion volume range of the triplet excitons is reduced significantly. When the phosphorescent dopant concentration is up to 1.0 wt %, which is ten times higher than the traditional single-EML-SD F/P hybrid WOLEDs, highly efficient white emission was still achieved with maximum total external quantum efficiency (EQE) of 23.8%, current efficiency (CE) of 56.1 cd A–1, and power efficiency (PE) of 62.9 lm W1–. The results will supply a novel method for obtaining high efficiency F/P hybrid WOLEDs in a SEML-SD architecture with easily controllable doping concentration.Keywords: hot exciton blue fluorophores; hybrid white organic light-emitting diodes; improved efficiency roll-off; superhigh phosphorescent dopant concentration;

•Two novel polymers based on diketopyrrolopyrrole as acceptor unit were synthesized and compared.•3,6-Di(thien-2-yl)pyrrolopyrroledione-based polymer showed a near linear spatial structure by theoretical calculation.•While 3,6-Di(furan-2-yl)pyrrolopyrroledione-based polymer exhibited a V-shaped spatial structure.•The enhanced performance was found that it is resulted from spatial structures manipulation.Two novel donor–acceptor conjugated polymers with 5H-dithieno[3,2-b:2',3'-d]pyran as a strong electron-donating unit and diketopyrrolopyrrole as electron accepting units were synthesized. The photophysical and electrochemical properties were investigated and compared. With the same donor unit, 3,6-di(thien-2-yl)pyrrolopyrroledione-based polymer showed an almost linear spatial structure, while 3,6-di(furan-2-yl)pyrrolopyrroledione-based polymer exhibited a V-shaped structure. The power conversion efficiency of solar cells based on 3,6-di(thien-2-yl)pyrrolopyrroledione-based polymer, with a high carrier mobility benefiting from almost linear backbone of 3,6-di(thien-2-yl)pyrrolopyrroledione-based polymer, was much higher than that of photovoltaic cells based on 3,6-di(furan-2-yl)pyrrolopyrroledione-based polymer. This work demonstrated a good example for enhancing efficiency of diketopyrrolopyrrole-based solar cells by adjusting the spatial structure.

•Novel phenanthrene isomers were synthesized and characterized.•Management of their intramolecular charge transfer (ICT) processes for violet-blue emitters.•The results were found to be good candidates as emitters for organic light emitting diodes (OLEDs).•The devices exhibit violet-blue light emissions with CIE coordinates of 0.16, 0.05) for m-PATPA at 100 cd/m2, respectively.•The results provide an efficient design strategy with strong donor (D) and acceptor (A) for violet-blue emitters.A couple of phenanthrene isomers were designed and synthesized by introducing strong D–π–A structure strategy to manage effectively their intramolecular charge transfer processes for violet-blue emitters. Their physical properties, including UV–vis, photoluminescence, thermal and electrochemistry, were systematically studied. The results were found to be good candidates as emitters for organic light emitting diodes (OLEDs). The devices based on them exhibit deep-blue light emissions with CIE coordinates of (0.15, 0.15) for p-PATPA and violet-blue (0.16, 0.05) for m-PATPA at 100 cd/m2, respectively. The violet-blue device shows good performance with external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 2.39%, 0.78 cd/A, and 0.72 lm/W, respectively. Furthermore, at the high luminescence, the device still indicated good performance with relative low efficiency roll-off. Our results here successfully provide an efficient design strategy with strong donor and acceptor for violet-blue emitters.A couple of phenanthrene isomers (PATPA) were designed and synthesized by introducing strong D–π–A structure strategy to manage effectively their intramolecular charge transfer (ICT) processes for violet-blue emitters.

•Two novel conjugated donor–acceptor polymers were synthesized and characterized.•By fine tuning side chains, polymers with low lying HOMO and high VOC of 1.02 V were obtained.•The VOC of the polymer containing 3-hexylthiophene was enhanced without sacrificing the JSC.•The VOC of 1.02 V is among the highest value for anthracene-based polymer solar cells reported.•This work exhibits a good way to regulate the molecular energy levels by fine tuning side chains.Two novel conjugated donor–acceptor polymers were synthesized by combining anthracene donor and benzothiadiazole acceptor with two different side chains (conjugated and non-conjugated). Their absorption spectroscopy, thermogravimetric analysis, electrochemical cyclic voltammetry, theoretical prediction, surface morphology, and photovoltaic performance were investigated. The resultant two-dimensional configuration showed good optical and electrochemical properties. By selectively introducing branched conjugated side chains and non-conjugated linear side chains on the polymer back-bone, the highest occupied molecular orbital levels are low lying which results in an increased open circuit voltage for polymer solar cells. The open circuit voltage of 1.02 V in this work was among the highest value for anthracene-based polymer solar cells ever. Our results suggest a good way to regulate the molecular energy levels by selecting appropriate side chains.

•Novel blue fluorescent emitters based on twisted anthracene derivatives were synthesized.•The efficiency of p-PABPI is three times of m-PABPI for the non-doped electroluminescent devices.•The performance of blue OLEDs can be significantly improved by tunable molecular configuration.Two novel twisted anthracene derivatives, 2-(4-(10-(phenanthren-9-yl)anthracen-9-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]-imidazole (p-PABPI) and 2-(3-(10-(phenan-thren-9-yl)anthracen-9-yl)phenyl)-1-phenyl-1H-phenanthro-[9,10-d]imidazole (m-PABPI), have been synthesized. Their photophysical and photochemical properties are also investigated systemically. The non-doped fluorescent organic light-emitting diodes are fabricated by using anthracene derivatives as the emitters. The maximum current efficiencies are achieved to be 3.98 and 1.32 cd A−1 and the maximum power efficiencies are 2.80 and 1.14 lm W−1, respectively. The external quantum efficiency maximum (EQEmax) is 3.61% and 1.33% for p-PABPI and m-PABPI. Intriguingly, the efficiencies of p-PABPI are almost three times larger than that of m-PABPI with only the different molecular configuration. The results revealed a new rule of molecular design based on anthracene derivatives for obtaining high performance blue emission materials.

Three novel donor–acceptor (D–A) conjugated copolymers for polymer solar cells (PSC) are presented in this work. By Stille coupling polymerization, indacenodithiophene (IDT), as an electron-rich unit, was conjugated with an electron-deficient unit of isoindigo (IID), which led to a novel alternative copolymer IDT–IID (P1). Two electron-deficient units, 2,1,3-benzooxadiazole (BO) and diketopyrrolopyrrole (DPP), were respectively introduced in the polymerization of P1, and two novel IDT-based D–A1–D–A2 random copolymers IDT–IID–IDT–BO (P2) and IDT–IID–IDT–DPP (P3) were obtained. Thermal property tests indicated that these molecules possess relative stability and are suitable for solar cell applications. Optical and electrochemical measurements revealed that the HOMO energy levels of the three copolymers were −5.46 eV, −5.34 eV, and −5.23 eV respectively, while the LUMO levels were almost kept stable around −3.56 eV and the low band gap levels led to complete absorption in the visible region. The PSCs based on these copolymers were fabricated with the structure of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al, and the photovoltaic properties disclosed the relatively high values of open circuit voltage (Voc) due to the low-lying HOMO energy levels of each copolymer. Hole mobility and atomic force microscopy (AFM) study were applied to improve the PSCs performance. Our work provides an efficient method to regulate the HOMO energy levels which will be beneficial for PSCs by synthesizing different conjugated copolymers.

An efficient synthetic approach to a series of benzothieno[2,3-b]thiophene (BTT) derivatives used as an important core with different bridge spacers is described. Thermal properties of the present compounds are stable: neither phase transition nor thermal decomposition was observed up to 300 °C. The adjacent molecule crystal stackings are shifted affording a nearly 1/3 intermolecular π-overlap. The OFETs based on BTTB exhibit excellent field-effect performances with a mobility of 0.46 cm2 V−1 s−1 and on–off current ratios larger than 107 at room temperature. All the results demonstrate these benzothieno[2,3-b]thiophene derivatives as promising materials for optoelectronic devices.

•Novel benzimidazole and triphenylamine donor–acceptor derivatives were synthesized and characterized.•The devices based on them show high efficiency 5.66% of EQEm for TPABBBI and 4.23% for TPABBI.•All of them show a low efficiency roll-off at high luminance and stable blue emission.•The results are demonstrated to be the simultaneous utilization of LE, ICT, and TICT.The simultaneous utilization of all charge-transfer excitons and local excitons is the pathway to obtain the high efficiency fluorescent organic light-emitting diodes (FOLEDs). Here, a twisted intramolecular charge transfer state (TICT-state), a planar intramolecular charge transfer state (ICT-state), and a locally excited state (LE-state) are demonstrated to enhance the occurrence of singlet excitons in the fluorescent emitters, which are based on benzimidazole and triphenylamine donor–acceptor derivatives. The synthesis, photophysics and electroluminescent (EL) performance are studied systematically. The fluorescence emitters (TPABBBI and TPABBI) with the special TICT and ICT characteristics realize the electron–hole (e–h) recombination via intramolecular conversion from charge-transfer excitons to radiative singlet exciton. The devices based on them show high efficiency (5.1 cd/A, 5.77 lm/W, 5.66% of EQEm for TPABBBI and 3.56 cd/A, 3.11 lm/W, 4.23% for TPABBI), low efficiency roll-off at high luminance and stable blue emission.A twisted intramolecular charge transfer state (TICT-state), a planar intramolecular charge transfer state (ICT-state), and a locally excited state (LE-state) are demonstrated to enhance the occurrence of singlet excitons in the fluorescent emitters, which are based on benzimidazole and triphenylamine donor–acceptor derivatives.

•Novel blue fluorescent emitters based on spirofluorene derivatives were synthesized and characterized.•The nondoped electroluminescent devices based on them show high efficiency and blue emissions.•The results are demonstrated to be tunable electroluminescence from sky-blue to deep-blue emission.Two novel benzimidazole-attached spiro[benzofluorene] derivatives, 2,2′-(spiro[benzo[c]fluorine-7,9′-fluorene]-5,9-diylbis(4,1-phenylene))bis(1-phenyl-1H-benzo[d]imidazole) and 2,2′-(spiro[benzo-[de]anthracene-7,9′-fluorene]-2′,3-diylbis(4,1-phenylene))bis(1-phenyl-1H-benzo[d]imidazole), were prepared by a Suzuki coupling reaction. Their photophysical and photochemical properties were studied systemically. The fluorescent organic light-emitting diodes were fabricated by using them as the emitters, all of them showed strong blue emission. Interestingly, from the benzoanthracene derived compound a high color purity was found with Commission de L'Eclairage 1931 chromaticity coordinates of (0.15, 0.10) and an efficiency of 1.96 cd/A. To the best of our knowledge, this is the first time to obtain a deep-blue emission with spiro[benzofluorene] derivative in a nondoped device.

•A template-free reaction system (FeCl2/H2O2/thiophene) is adapted to prepare polythiophene microspheres.•The microspheres show uniform size, good thermal stability, solubility and spherical shape.•Well-dispersed polythiophene-containing waterborne epoxy coatings for Q235 steel are prepared.•After 360 h of immersion, the impedance values remain at higher than 1 × 106 Ω cm2.•The coatings have low corrosion current (2.297 × 10−8 A cm−2).A facile, template-free method to prepare polythiophene microspheres with uniform size and well spherical shape is successfully performed, using anhydrous FeCl2 as catalyst and H2O2 as oxidant by a one-pot chemical oxidation polymerization. The structure and morphology of polythiophene nanoparticles is characterized by IR, SEM and TEM. Polythiophene nanostructures exhibit good morphology of microspheres with a very narrow particle size distribution. By fine tuning the reaction conditions, different sizes and nanostructured polythiophene can be obtained. The corrosion protection property of polythiophene microspheres-containing coatings on mild steel is investigated by electrochemical impedance spectroscopy (EIS) technique in 3.5 wt% NaCl aqueous solution. The results indicated that the waterborne polythiophene microspheres-containing coatings (polythiophene content, 0.6 wt%) could offer high protection because the impedance values remained at higher than 1 × 106 Ω cm2 after 360 h. All the results are compared with these of the pure waterborne epoxy coatings on mild steel.Polythiophene microspheres with uniform size and low PDI were prepared by a facile, one-pot method. Owing to its uniform and small particle size, polythiophene microspheres can be well dispersed to be utilized in waterborne corrosion protection coatings. The results showed the polythiophene-containing waterborne coatings could offer high protection with impedance values remained at higher than 1 × 106 Ω cm2 after 360 h of immersion in 3.5 wt% NaCl aqueous solution. And the corresponding low corrosion current (2.297 × 10−8 A cm−2) showed much better protective effect than pure waterborne epoxy coatings.

In order to guide the synthesis of new materials with low band gaps, quantum-chemical methods have been increasingly applied to predict the band gaps of conjugated polymers. Softwares such as Material Studio, Gauss View, Gauss 03 and Gauss 09 calculation program were used in this paper. Semi-empirical AM1 method was applied to calculate the optimal geometric structure of selected three benzo[1,2-b:4,5-b\('\)]dithiophene homopolymers, namely PBDTV, H2 and H3. Using the generalized density function theory based on B3LYP/6-31G*, B3LYP/6-311G* and M062X/6-311G* level calculation of polymers’ band gaps. The results indicate that whether there is enough interspace between adjacent subunits, long alkoxy side chain is advantageous to the band gap decrease, and otherwise it will bring steric hindrance to destroy the coplanarity of polymer chain which is disadvantageous to the band gap decrease. The band gaps of polymers mainly depends on the molecular structure, generally speaking, the more coplanarity of main chain, smaller dihedral angle, smaller difference between the bond length of single and double bonds in the main chain, resulting in narrower band gap.

Rational design and synthesis of polymeric semiconductors is critical to the development of polymer solar cells (PSCs). In this work, a new series of benzodithiophene–difuranylbenzooxadiazole-based donor–acceptor co-polymers—namely, PBDT-DFBO, PBDTT-DFBO, and PBDTF-DFBO, with various side groups—have been developed for bulk-heterojunction PSCs. These side-group substituents provide the opportunity to tailor the opto-electrical properties of the polymers. In addition, we show that the reduction of the bandgap of polymers and the enhancement of charge mobility in the devices can be accomplished concurrently by substituting the alkylthienyl side group with its furan counterpart. In the preliminary investigation, one could obtain PSCs with a power conversion efficiency (PCE) of 2.1% for PBDT-DFBO with an alkoxyl side chain, 2.2% for PBDTT-DFBO with an alkylthienyl side group, and 3.0% for PBDTF-DFBO with an alkylfuranyl side group. Further optimizing the performance of the devices was conducted via a simple solvent treatment. The PSCs based on PBDTF-DFBO:PC71BM could even achieve 7.0% PCE, which exhibited an enhancement of 130%. To the best of our knowledge, the value of 7.0% is the highest efficiency for furan-containing PSCs to date and is also comparable with the hitherto reported highest efficiency of the single junction PSCs. Through a combination of testing charge transport by the space-charge limited current (SCLC) model and examining the morphology by atomic force microscopy (AFM), we found that the effects of solvent treatment on the improved performance originate from higher and more balanced charge transport and the formation of fiberlike interpenetrating morphologies, which are beneficial to the increase of short-circuit current density (Jsc) and fill factor (FF). This work demonstrates a good example for tuning absorption range, energy level, charge transport, and photovoltaic properties of the polymers by side-chain engineering and the solvent treatment can offer a simple and effective method to improve the efficiency of PSCs.Keywords: donor−acceptor conjugated copolymer; polymer solar cells; side group engineering; solvent treatment;

•Well-defined 3,6-PCZ was firstly prepared.•2,7-PCZ with a molecular weight 10,000 and low polydispersity of 1.27 was prepared.•The success of polymerization dependent on the N-substituents of monomer solubility.Polycarbazoles (PCZ) are well-studied class of polymers with good electrical and photoactive properties. Here, we have prepared the well-defined 3,6-PCZ with a molecular weight of 6148 and low polydispersities of 1.18. We also used 2,7-dibromo-9-(heptadecan-9-yl)-9H-carbazole as monomer to increase the solubility of the polymer. The 2,7-PCZ with a high molecular weight over 10,000 and low polydispersity of 1.27 was prepared successfully.Graphical AbstractPolymerization of the 3,6-dibromo-9-octyl-9H-carbazole with Ni(dppe)Cl2 affords the polymer with a molecular weight of 6148 and a low polydispersity of 1.18. These good results imply that catalyst-transfer Kumada coupling polymerization has generality for the synthesis of well-defined 3,6-polycarbazoles.

A new A–D–A small molecule involving anthradithiophene as a donor and benzothiadiazole as an acceptor unit has been synthesized by Stille coupling reaction. Its thermal, optical and electronic properties, hole mobility and photovoltaic properties have been fully characterized. The resulting material shows a broad absorption range (300–750 nm), a low band gap (1.59 eV) and a moderate hole mobility (8.81 × 10−4 cm2 V−1 s−1). We used the new small molecule blended with PC71BM as the active layer to fabricate solution-processed organic solar cells (OSCs), and employed a variety of post-treatment methods to optimize the device performance. With the help of polar solvent exposure, the highest power conversion efficiency (PCE) of 0.55% was obtained. These results would supply useful information to understand the relationship between molecular structure and photovoltaic properties of anthradithiophene/benzothiadiazole-based OSCs.

A series of new butterfly-shaped thieno[3,2-b]thiophene oligomers with phenyl and thiophene units were synthesized through Suzuki coupling and Stille coupling reactions. The optical and thermal properties of these materials can be tuned by varying both substituents and the conjugation length. The crystal structures have been determined and showed a syn- or anticlinal conformation in the crystal of molecule 4. The electronic properties of the monomers and their electropolymerization ability are discussed and rationalized as a function of their molecular structure. Moreover, stable cross-linked conjugated polymers were formed by electropolymerization.

•Novel host materials based on arylamine and phenanthroimidazole moieties.•High triplet energy hosts for phosphorescent OLEDs.•Highly efficient green phosphorescent OLEDs.Two novel host materials, 2-(4,4″-di(9H-carbazol-9-yl)-[1,1′:3′,1″-terphenyl]-5′-yl)-1-(4-(trifluoro-methyl)phenyl)-1H-phenanhro[9,10-d]imidazole (DCzBPI) and N4,N4,N4″,N4″-tetraphenyl-5′-(1-(4-(trifluoromethyl)phenyl))-1H-phenanthro-[9,10-d] (DTPABPI), were designed and synthesized. The electroluminescence (EL) characteristics by using them as host materials were investigated. Results were found both of them showed good performance, especially for DCzBPI. The maximal external quantum efficiency is up to 21.2% and the brightness is up to 63,610 cd/m2 with current efficiency of 53.8 cd A−1.

Two new alkylfuranyl-substituted conjugated donor–acceptor polymers—PBDTF-DPP and PBDTF-DPPF—were designed and synthesized. To compare the properties of the new polymers, PBDT-DPP and PBDT-DPPF with alkoxy side chains were also synthesized. The photophysical and electrochemical measurement demonstrated that the alkylfuranyl-substituted polymers had smaller optical band gaps, broader absorption range, and lower HOMO energy levels, thus leading to a larger short current density (Jsc) and higher open circuit voltage (Voc) in photovoltaic devices. Under the same fabricating conditions, the efficiency of the polymer solar cells (PSCs) based on PBDTF-DPP and PBDTF-DPPF reached 3.5% and 5.1%, respectively, whereas PSCs based on PBDT-DPP and PBDT-DPPF only showed an efficiency of 1.0% and 2.9%. After thermal annealing, the efficiency of the PSCs based on PBDTF-DPPF:PC71BM further achieved as high as 6.1%. The results indicate a great potential for largely improving the efficiency of the PSCs by replacing alkoxy with alkyfuranyl group and the building block BDTF in creating exceptional performance materials for PSCs.

•Crystalline TiO2 films with different structures were synthesized by sol-gel method.•Power conversion efficiency greatly enhanced by tuning the TiO2 films' structures.•Optimized devices achieved a power conversion efficiency of 3.56%.•Optimized devices present excellent stability performance in argon atmosphere.Inverted polymer solar cells using TiO2 film as electron transporting layer were fabricated with the structure of fluorine-doped tin oxide/TiO2 films/poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Ag. By tuning the crystalline structure of TiO2 films, the photovoltaic performance of the devices was remarkably enhanced. TiO2 was prepared by sol-gel method and their structures, morphologies and transmittance were characterized by X-ray diffraction, scanning electron microscope, and UV-visible spectrophotometer. Interestingly, for TiO2-3 film, which was prepared with tetrabutyl titanate, acetyl acetone and ethanol in a ratio of 1:0.5:6, the open-circuit voltage and fill factor of the device were up to 0.6 V and 64.8%, respectively, and the power conversion efficiency of TiO2-3 film was achieved up to 3.56% with the current density of 9.18 mA/cm2 under an AM 1.5 G (100 mW/cm2) irradiation intensity. In the meanwhile, the stabilities of these devices were also studied and results showed that our work was better than the corresponding devices of conventional structure.

A novel electrophosphorescent material based on a biscyclometalated iridium(III) complex of the N,N-diphenyl-4′′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-amine ligand, named Ir(TPABPBI)2(acac), has been synthesized and its application in organic light emitting devices (OLEDs) was studied. Highly efficient, solution-processed, single-layer, electrophosphorescent diodes utilizing the complex have been prepared and characterized. In these devices, the high triplet energy poly(9-vinylcarbazole) (PVK) is used as a host polymer doped with 2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) employed for electron transport. When the doping concentration of Ir(TPABPBI)2(acac) is up to 4%, devices with a current efficiency of 30.0 cd A−1 corresponding to an EQE of 15% can thus be achieved, along with the Commission de l'Eclairage 1931 chromaticity coordinates of (0.507, 0.486). More importantly, the yellow phosphorescence can be achieved without the generation of excimer emission. Such devices exhibit a very broad and featureless peak at ca. 568 nm with a wide full spectral width at half maximum (FWHM) of 83 nm. These results render Ir(TPABPBI)2(acac) a promising organic phosphor for applications in yellow OLEDs, especially for large-area, highly efficient and cheap yellow PhOLEDs.

A blue fluorophore of N,N-diphenyl-4′′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-amine (BBPI) was utilized as the blue fluorescent emitter and the host of a phosphorescent emitter to fabricate highly efficient fluorescent/phosphorescent (F/P) hybrid white organic light-emitting diodes (WOLEDs) in a single- or multi-emission-layer architecture. For the single-emission-layer WOLEDs consisting of only the blue emitter BBPI and yellow complementary phosphorescent emitter PO-01 in the emission layer, a maximal current efficiency (CE) of 49.1 cd A−1, power efficiency (PE) of 52.0 lm W−1, and external quantum efficiency (EQE) of 16.3% were achieved by modulating the dopant concentration, indicating efficient singlet and triplet exciton separation and utilization ability in the emission layer. An improved EQE of 17.1%, broader spectral coverage, and higher color rendering index (CRI) were achieved by inserting a non-doped blue emission layer of BBPI and a green emission layer of CBP:Ir(PPy)3. A further improved EQE of up to 19.7% could be achieved when an orange-red phosphorescent emitter PQ2Ir was used instead of PO-01, and it is one of the best reported values for the F/P hybrid WOLEDs.

A series of novel benzophenone-based small molecular cathode interfacial materials with different polar groups including hydroxyl groups, neutral amino groups, amino N-oxide, and sulfobetaine ions were synthesized for PTB7:PC71BM-based polymer solar cells between the active layer and Al electrode. The photovoltaic properties of the devices with these interfacial materials were studied. The differences in interface modification performance of hydroxyl and amino interfacial materials were investigated for the first time. The devices with a solution-processed amino N-oxide-based interlayer showed a PCE of 9.34% with the highest short-circuit current density and fill factor by reducing the series resistance and charge recombination compared to the devices with the other interlayers in this work. The study of structure–property relationships proposes the significant guidance for the design of efficient cathode interface materials in organic solar cells.

An efficient synthetic approach to a series of benzothieno[2,3-b]thiophene (BTT) derivatives used as an important core with different bridge spacers is described. Thermal properties of the present compounds are stable: neither phase transition nor thermal decomposition was observed up to 300 °C. The adjacent molecule crystal stackings are shifted affording a nearly 1/3 intermolecular π-overlap. The OFETs based on BTTB exhibit excellent field-effect performances with a mobility of 0.46 cm2 V−1 s−1 and on–off current ratios larger than 107 at room temperature. All the results demonstrate these benzothieno[2,3-b]thiophene derivatives as promising materials for optoelectronic devices.

A novel electrophosphorescent material based on a biscyclometalated iridium(III) complex of the N,N-diphenyl-4′′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-amine ligand, named Ir(TPABPBI)2(acac), has been synthesized and its application in organic light emitting devices (OLEDs) was studied. Highly efficient, solution-processed, single-layer, electrophosphorescent diodes utilizing the complex have been prepared and characterized. In these devices, the high triplet energy poly(9-vinylcarbazole) (PVK) is used as a host polymer doped with 2-(4-biphenylyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) employed for electron transport. When the doping concentration of Ir(TPABPBI)2(acac) is up to 4%, devices with a current efficiency of 30.0 cd A−1 corresponding to an EQE of 15% can thus be achieved, along with the Commission de l'Eclairage 1931 chromaticity coordinates of (0.507, 0.486). More importantly, the yellow phosphorescence can be achieved without the generation of excimer emission. Such devices exhibit a very broad and featureless peak at ca. 568 nm with a wide full spectral width at half maximum (FWHM) of 83 nm. These results render Ir(TPABPBI)2(acac) a promising organic phosphor for applications in yellow OLEDs, especially for large-area, highly efficient and cheap yellow PhOLEDs.

As a promising option out of all of the well-recognized candidates that have been developed to solve the coming energy crisis, polymer solar cells (PSCs) are a kind of competitive clean energy source. However, as a convenient and efficient method to improve the efficiency of PSCs, the inherent mechanism of the interfacial modification was still not so clear, and interfacial materials constructed with new units were limited to a large degree. Here we present a new kind of interfacial material consisting of AIE units for the first time, with an efficiency of 8.94% being achieved by inserting TPE-2 as a cathode interlayer. This is a relatively high PCE for PC71BM:PTB7-based conventional PSCs with a single-junction structure. Different measurements, including TEM, AFM, SEM, GIXRD, UPS, SKPM, and SCLC, were conducted to investigate the properties in detail. All of the obtained experimental results confirmed the advantages of the utilization of new interfacial materials with AIE characteristics in polymer solar cells, thus providing an additional choice to develop new organic cathode interfacial layers with high performances.

A novel non-conjugated small-molecule electrolyte was invented as a cathode interlayer in PTB7:PC71BM-based polymer solar cells (PSCs). We discovered a significant synergy effect for improving the device efficiency between methanol treatment and the interlayer. The methanol treatment mainly contributed to the open-circuit voltage, while the interlayer primarily enhanced the short-circuit current and fill factor. Under the effective synergy effect, power conversion efficiencies (PCEs) of PTB7:PC71BM-based PSCs were largely improved from 3.89% to 9.79% for conventional PSCs and from 7.34% to 9.10% for inverted PSCs. Our findings create a new path of interfacial modification for highly efficient PSCs.

Highly efficient organic light-emitting diodes (OLEDs) with simplified device structures are widely desired for both scientific research and industrial applications. However, a very limited number of simplified OLEDs have been reported to date. In this work, two multifunctional blueish green emitters, BPTPETPAI and 2TPETPAI, are designed and synthesized. Owing to the presence of a tetraphenylethene (TPE) moiety, their aggregation induced emission (AIE) properties are also investigated. High photoluminescence efficiencies of the two compounds in non-doped films render them good emitters for non-doped devices. Multilayer non-doped devices based on these emitters achieve maximum external quantum efficiencies (EQEs) and current efficiencies (CEs) of 3.13% and 6.14 cd A−1 as well as 3.25% and 6.70 cd A−1 for BPTPETPAI and 2TPETPAI, respectively. Given their shallow highest occupied molecular orbital (HOMO) energy levels, both emitters can also be used as hole injection and hole transporting materials. Based on this, single layer devices show even higher efficiencies with extremely low efficiency roll-off, achieving maximum CEs as high as 7.12 cd A−1 and 7.80 cd A−1 using BPTPETPAI and 2TPETPAI, respectively. These results demonstrate a bright prospect for the development of highly desired multifunctional emitters as well as simplified OLEDs with significant reduction in the fabrication cost of the device.

A novel non-conjugated small-molecule zwitterion is developed as a cathode interfacial material to enhance the electron transfer and collection properties of high-performance PSCs. The devices show significantly increased performance with power conversion efficiencies up to 9.51%. It is noteworthy that the results here provide significant scientific insights into further improvement of interfacial modification and performance of polymer solar cells.