•Three novel trichromatic iridium complexes based on 2-(4-bromophenyl)-1-hydrogen-benzimidazole are obtained and the phosphorescent quantum efficiencies for Ir(pbi)3, (pbi)2Ir(acac) and (pbi)2Ir(phen) in CH2Cl2 solution are found to be 9.35, 10.63 and 25.14 %.•Excited-state lifetimes for these iridium complexes are in the microsecond regime (0.13 0.55 us), the faster decay times suggest that the emitting state has triplet character with strong spin–orbital coupling.•The trichromatic iridium complexes not only can be directly used as luminescent materials, but also can be used as reactive monomers for the development of trichromatic polymer luminescent materials owing to the bromine atom in the structure by the Suzuki polycondensation.The tris-cyclometalated iridium complex Ir(pbi)3 was synthesized regarding 2-(4-bromophenyl)-1-hydrogen-benzimidazole(pbi) as cyclometalated ligand and the heteroleptic iridium complexes (pbi)2Ir(acac) and (pbi)2Ir(phen) were prepared through the ancillary ligands acetylacetone(acac) and 1,10-phenanthroline(phen), respectively. Wherein the complex Ir(pbi)3 gives the maximum emission peak of 436 nm at 365 nm excitation and color coordinate of (0.173, 0.144) as a blue light-emitting. The complexes (pbi)2Ir(acac) and (pbi)2Ir(phen) present the maximum emission wavelength of 536 nm and 616 nm and color coordinates (0.301, 0.591) and (0.630, 0.345) respectively corresponding to the green and red emission. The phosphorescent quantum efficiencies for Ir(pbi)3, (pbi)2Ir(acac) and (pbi)2Ir(phen) in CH2Cl2 are found to be 9.35%, 10.63% and 25.14% respectively, and their quantum efficiencies in powder are found to be 3.27%, 2.74% and 12.21% respectively. Excited-state lifetimes for these iridium complexes are in the microsecond regime(0.13–0.55 us). Such long-lived excited states clearly suggest that the emitting state has triplet character. The cyclic voltammetry curves showed the HOMO energy levels of the trichromatic complexes and the LUMO energy levels were obtained combining the HOMO energy levels and optical band gaps. The optimal molecular structures and the HOMO and LUMO orbital energy levels of the complexes were figured up through DFT theory Gaussian simulation, indicating the basic numerical coincide of theory and experimental values.

Three D–A low-bandgap polymer-based benzo[1,2-b:4,5-b′]dithiophene (BDT) and thieno[3,4-b]pyrazine (TP) unit with different substituents were synthesized using Stille coupling. The substituent effects were explored. It is found that attaching the phenyl group at the 2,3-positions of thienopyrazine unit is beneficial to good coplanarity and regularity of molecular packing. Meanwhile, attaching the longer alkoxyl side chain at BDT unit or phenyl group at the 2,3-positions of thienopyrazine unit had the relatively deep HOMO (LUMO) energy levels. The three D–A polymers showed good thermal stability and exhibited broad absorption, low bandgap, and order packing structure. As a result, the highest PCE of 1.50 % was achieved for the polymer P2 with the substituents, including hexyldecyloxyl at the BDT unit and phenyl at the TP unit.

A series of novel praseodymium(Pr)-coordinated polymers with fluorene, phthalimide and bipyridine moieties in the main chain were synthesized via a coordination reaction and palladium-catalyzed Suzuki coupling polycondensation. Their structures, optical features and memory performance have been well studied. A resistive switching device with the configuration of ITO/polymer/Al was constructed using a spin-coating process. The device exhibits nonvolatile write-once-read-many-times (WORM) memory behavior. Based on the electrochemical properties and theoretical calculations of the polymers, the effects of the phthalimide moiety and neutral Pr complex on the polymer memory device performance were investigated. Our work offers valuable clues on the development of polymer memory devices.

•A series of naphthalene diimide (NDI)-based random terpolymers x-NDI were synthesized with variation of T-NDI/Se-NDI ratios via random polymerization.•By tuning the T-NDI/Se-NDI ratios, the crystallinity, film morphology, charge transport and photovoltaic performance of the fabricated polymer solar cells can be fine-tuned.•The device based PBDT(T)TPD/0.5-NDI exhibited a high PCE of 5.4% and a high Voc of 1.05 V.•Our work presents a simple and effective method to obtain acceptor matching with the chosen donor leading to efficient PSCs.A series of naphthalene diimide (NDI)-based random terpolymers x-NDI as polymer acceptors were synthesized with variation of T-NDI/Se-NDI ratios in polymers, which x-NDI were composed of naphthalene diimide with an octyldodecyl branched chain acceptor units and randomly distributed thiophene (T) and selenophene (Se) donor units. Meanwhile, the reference alternating copolymers (P(NDI2OD-T) and P(NDI2OD-Se)) were synthesized. The structure-property relationships of the random terpolymers were systematically studied. The effects of T-NDI/Se-NDI ratios on the absorption, energy levels, crystallinity, film morphology, charge transport and photovoltaic performance of the fabricated polymer solar cells were investigated. The acceptor 0.5-NDI with proper crystallinity was fully miscible with the chosen donor polymer PBDT(T)TPD, and formed the nanostructured blend. Compared to that of PBDT(T)TPD/P(NDI2OD-T) or PBDT(T)TPD/P(NDI2OD-Se) solar cells, the PBDT(T)TPD/0.5-NDI solar cells exhibited an improved short-circuit current density (Jsc) of 9.1 mA/cm2, a high open circuit voltage (Voc) of 1.05 V and enhanced power conversion efficiency (PCE) of 5.4%. Our work demonstrates that the development of random terpolymers is a simple and effective method to obtain polymer acceptor matching with the chosen polymer donor leading to efficient PSCs.Download high-res image (238KB)Download full-size image

Non-conjugated copolymers with iridium complex and carbazole groups and polyhedral oligomeric silsesquioxane (POSS) moieties as pendant groups were synthesized by free radical copolymerization. The luminescent properties of the polymeric hybrid materials containing the carrier-transporting units (carbazole groups), phosphorescence units (iridium complex) and nano-scale particles (POSS) were studied to explore the effect of POSS on the luminescence of non-conjugated copolymer hybrid materials. The results showed that the copolymers with POSS exhibited good solubility in common organic solvents and better film-formation property. The photoluminescence decays of all copolymers in solid state were bi-exponential indicating the presence of more than one emissive species, which was attributed to intra-polymer chromophore interactions. The luminescence lifetimes of the copolymers were 0.28–1.60 μs, indicating phosphorescence emission. The luminescence properties of the copolymers were improved significantly by incorporating bulky POSS into the polymer side-chain, and the maximum quantum efficiency was found to be 52.4% for ternary copolymer PCz-Ir1.0-POSS6, which was more than six times than that of binary copolymer PCz-Ir1.0 (Φpl = 7.7%). The grafted bulky POSS can enhance the thermal stability, however, POSS had no influence on the electrochemical properties of the copolymers.

The non-emissive benzene ring and green-emissive arylmaleimide are employed as two independent cores to construct dual-core white star-shaped polymers (DC-PFMs). Due to the totally star-shaped structure, DC-PFMs display a higher quantum yield and electroluminescence efficiency for a more efficient energy transfer from the host to the guest than traditional single-core polymers (SC-PFMs).

Full-solution processed, flexible, top-emitting polymer light-emitting diodes (PLEDs) are fabricated by using low-cost and high-quality printed Ag electrodes. Employing a composite cathode (Ag/ZnO/PEI) and bi-layer anode of WO3/PH1000, the resulting devices exhibit quite comparable device performances to the conventional PLEDs, remarkable flexibility and great potential for large-area production.

A series of novel praseodymium (Pr)-bonded polymers were successfully synthesized via the coordination reaction and palladium-catalyzed Suzuki coupling reaction of 2,7-dibromo-9,9′-dioctylfluorene and different amounts of 5,5′-dibromo-2,2′-bipyridine. The resulting polymers were characterized by 1H-NMR and GPC. The photoluminescence (PL) and electroluminescence (EL) properties of the resulting polymers were studied to explore the effects of the Pr triisopropyloxide. The results showed that the incorporation of Pr into the polymers caused better coplanarity and effective intermolecular or intramolecular interaction, leading to the higher emission intensity at long-wavelength. Further, it was also found that the emission light color could be tuned from blue to green by introduction of a small amount of Pr into the polymer main chain. A single-layer green emitting EL device based on PF(BipyPr)6 with 6 mol% Pr content was fabricated. The device had a low turn-on voltage of 6 V, a brightness of 705.3 cd·m−2, the maximum luminous efficiency of 1.53 cd·A−1 and the maximum power efficiency of 0.69 lm·W−1.

•Lateral-chain and star-like type single white polymers were designed and synthesized.•Simple diarylmaleimides were used as guest to construct novel single white polymers.•Star-like single white polymer SPF-PF02 shows the current efficiency of 10.30 cd/A.Two kinds of novel single white polymers, lateral-chain type and star-like type, were designed and synthesized by introducing di(p-methoxyphenyl)maleimide (λem = 540 nm) or dithienylmaleimide (λem = 558 nm) guest into the side chain of linear polyfluorene (LPF-TMs and LPF-PMs), and diphenylmaleimide (λem = 500 nm) guest into the core of star-like polyfluorene (SPF-PMs). By adjusting the feed ratio of maleimide and fluorene units, the resulting single white polymers exhibited a dual emission including blue emission (ca 430 nm) from polyfluorene host and yellow (ca 536 nm) emission from diarylmaleimide guest. Their electroluminescent properties were investigated in the single-emitting-layer devices fabricated by solution process with the configuration of ITO/PEDOT:PSS/polymer/TPBI/LiF/Al. Compared with main-chain type polymers, LPF-PMs and SPF-PMs displayed better electroluminescent performance with the maximal current efficiency of 8.77 cd/A and 10.30 cd/A, respectively. Due to the balanced blue and yellow emission, LPF-TM03 containing 0.3% guest get the relatively pure white light with CIE coordinates value of (0.31,0.33). The results indicate that diarylmaleimide is a kind of utility guest to construct easily synthesized, structurally diverse and highly efficient white polymers.Download high-res image (113KB)Download full-size image

A low-cost, hyper-branched, carbazole-based polymer (HB-Cz) was designed and synthesized by a facile “A3 + B2” one-pot Suzuki polycondensation reaction. Due to the hyper-branched structure and carbazole unit, HB-Cz is a promising candidate for a hole-transporting material, which was confirmed in perovskite solar cells (PVSCs) with a configuration of ITO/TiO2/MAPbI3/HB-Cz/Ag. The films of poly-(3-hexylthiophene) and linear poly[N-(1-octylnonyl)-9H-carbazole-2,7-diyl] were also used as hole-transporting layers (HTLs) in the reference devices. Time-resolved photoluminescence spectra indicate that HB-Cz has the fastest charge regeneration. Electrochemical impedance spectroscopy revealed that HB-Cz could reduce carrier recombination effectively, improving the open circuit voltage and fill factor of the PVSCs. A PCE of 14.07% obtained from the HB-Cz-based device was much higher than those of devices based on P3HT (9.05%) and PCz (6.60%), and this is attributed to the superior hole-transporting property and surface smoothing effect of the HB-Cz HTL.

•A low temperature solvent annealing of PbI2 without any additives was developed.•Pinhole-free and uniform MAPbI3 thin films with microscale grain sizes was obtained.•PCE increased to 12.12% by 42.7%, compared with that of the control device.•Highly reproducible and hysteresis-less inverted planar PVSCs demonstrated.Highly reproducible and photocurrent hysteresis-less inverted planar perovskite solar cells were demonstrated by a modified solvent annealing method in a two-step solution deposition (modified method). PbI2 film was annealing at 40 °C using the residue solvent after spin-coating, which facilitated the subsequent CH3NH3PbI3 perovskite active layer with high photovoltaic properties. The resulting device present a power conversion efficiency of 12.12%, which increased 42.7% compared with that of the control device fabricated as literatures.A simple solvent annealing method was utilized in the inverted planar PVSCs with a structure of ITO/PEDOT:PSS/MAPbI3/PCBM/Ca/Al. The optimized MAPbI3 active layer not only endowed the increased PCE but also the highly reproducible and photocurrent hysteresis-less properties to the devices.

•A series of diarylmaleimide dyes with different N-substituent were synthesized.•Switch from yellow to red emission results from a crystal-to-crystal transition.•Piezochromic fluorescence under a low hydrostatic pressure (0–25 MPa) was observed.•Rewritable data recording including solvent writing and vapor writing were explored.•Nanoparticles of the dyes in aqueous solution can effectively detect picrates and changes in pH.A series of carbazole-based diphenyl maleimide dyes with different N-substituent were synthesized through an Ullmann reaction in high yields. The dyes exhibit an intense emission in the solid state for their twisted conformation fixed by weak intermolecular interactions, resulting in the hindrance of the internal rotations. Their solid-stated emission wavelength and intensity are sensitive to external stimuli (like heat, pressure and vapor), due to a crystal-to-crystal or crystal-to-amorphous phase transition. Based on the multi-stimuli-responsive fluorescence properties of the N-benzyl analogue, two kinds of applications were explored. One is rewritable data recording processes including solvent writing and vapor writing. The other is sensing for low hydrostatic pressure (0–25 MPa). Interestingly, nanoparticles of the dyes formed in aqueous solution could effectively detect explosive and pH changes. A 15 ppm concentration of picric acid quenched the fluorescence of the N-methyl analogue with the detectable limit calculated to be 0.13 ppm. The N-methyl analogue also showed a different emission color and intensity over the pH range 12–14, which originated from the hydrolysis of the dye molecules in the strongly basic solution.

•Highly pure star-like polymers were obtained by using new construction strategy.•Simple non-emissive core replaced emissive one synthesized by complex procedure.•The formation of linear polyfluorene can be effectively suppressed in the new system.•The performance of white device was improved substantially by annealing at 140 °C.•Tight molecular stacking was responsive for the high efficiency of annealed devices.A series of novel star-shape like white polymers were synthesized by employing the benzene as the core, and incorporating different amount of bis (4-methoxyphenyl) maleimide guest onto the side-chain of the polyfluorene (PF) arm host. Due to the large feed ratio of core, such a construction strategy could efficiently avoid or suppress the formation of linear PF which always existed in the previous star-like polymers employing guest as core. When applied to the single emitting layer devices fabricated by solution spin-coating method, the efficiency of the devices enhanced gradually with the amount of guest increasing from 0.01% to 2%. The device performance was further improved substantially by annealing at 140 °C. A typical device base on P1 containing 1% dopant exhibited maximal luminous efficiency of 6.13 cd/A. Interestingly, the increase of efficiency is not originated from the self-dopant effect of α or β crystalline phase, which was always produced by thermal treatment at 120 °C in linear or previous star-like polyfluorenes. Morphology analysis disclosed that annealing made the polymeric molecules stack become closer, consequently resulting in a more effectively charge transfer and energy transfer from host to guest. As a result, the compact molecular stacking of the star-shape like polymers should be responsive for the high efficiency of annealed devices. The results would be conducive to design new star-shape like polymers with more arms, and improve the performance of white devices.

A series of benzamide-based diphenyl maleimide derivatives 2a–d with strong crystallization-induced emission (CIE) activity were synthesized and investigated. 2a–d are almost non-emissive in solutions and amorphous films, but intensely and greenly emissive in crystalline powders and crystals with a quantum yield of 53% and 80%, respectively. The results of X-ray diffraction analysis and theoretical calculation demonstrate that the intramolecular hydrogen bond between CO and NH groups formed in the excited state of 2 quenches the fluorescence, resulting from the rotation of benzamide groups in their solution and amorphous states. However, it would not happen in their crystalline sates for the locked conformation. Thus, the formation and inhibition of the hydrogen bonding in the excited state may be responsible for their CIE activity. Interestingly, the florescence of the 2d solid can be switched between on/off states by external stimuli including grind, heat, solvent vapor, and acid/alkali, which was utilized to develop three kinds of new technologies for rewritable information storage and security ink.

A novel Λ-shaped donor–π–acceptor–π–donor molecule BCPMM with AIEE, CIEE and polymorphism-dependent fluorescence properties was developed. The emission of BCPMM in solid states could be tuned by an external stimulus, which was utilized to construct five simple logic gates and more than ten kinds of sequential combinational logic systems.

•Small molecule 3 and polymer 5 based on perylene diimide and thienylenevinylene were synthesized.•Compounds 3 and 5 were used as acceptors to fabricate fullerene-free polymer solar cells.•Polymer solar cells based on 5 exhibited higher efficiencies (1.00%) than those of 3 (0.69%).A small molecule and a polymer based on perylene diimide and thienylenevinylene were designed and synthesized. Both small molecule and polymer exhibited excellent thermal stability with decomposition temperatures of >400 °C and strong absorption in the visible region (300–800 nm). These two compounds showed highest occupied molecular orbital levels of −5.57 and −5.70 eV and lowest unoccupied molecular orbital levels of −3.72 and −3.67 eV, respectively. Solution processed fullerene-free polymer solar cells based on the small molecule acceptor and the polymer acceptor afforded power conversion efficiencies of up to 0.69% and 1.00%, respectively. Comparative studies of the absorption, energy levels, charge transport, morphology and photovoltaic properties of the small molecule and polymer were carried out.

•The novel fluorescent sensors based on amide showed high selectivity for F− and CN−.•The interaction for F− and CN− was hydrogen bond and addition reaction, respectively.•The selectivity was improved further by replacing trifluoroacetamide with acetamide.•The sensitivity was improved further by introducing sensors into polyfluorene.•The copolymers exhibited ratiometric fluorescence properties upon F− or CN−.A series of diarylmaleimide derivatives and polymers based on amide group were designed and synthesized to detect anions selectively and sensitively. Three bisindolylmaleimide derivatives (FAM-p, FAM-m and FAM-o) employing trifluoroacetamide as receptor exhibited strong fluorescent quenching upon fluoride and cyanide. Trifluoroacetamide receptor was replaced by acetamide to obtain other two derivatives (AM-p and AM-o) which showed higher selectivity than FAMs with sensing for only fluoride. The diarylmaleimide derivatives were introduced into the backbone of polyfluorene by Suzuki reaction to prepare polymer PFAM and PAM with same sensing selectivity for anions as FAM and AM, respectively. PFAM and PAM were found to be ratiometric fluorescence sensors for a fluorescence resonance energy transfer (FRET) from fluorene segments to diphenylmaleimide units. The experimental and DFT/TDDFT calculation results demonstrated that the interaction mechanism of FAMs with F− and CN− was hydrogen bond interaction and nucleophilic addition reaction, respectively.

•Present a simple and effective method to prepare the regular D–A1–D–A2 copolymers for solar cells.•The synthesized copolymers exhibit broad absorption, narrow band gap and order packing structure.•The effect of dodecyl substituent on the properties of the copolymers was explored.•The relationship between the molecular weight and photovoltaic performance in copolymer P1 was revealed.•This work is expected to be valuable for simple synthesis of the regular D–A1–D–A2 copolymers.Two regular D–A1–D–A2 copolymers were synthesized via direct arylation polycondensation. In these copolymers, diketopyrrolopyrrole and benzothiadiazole were used as the acceptor units, while oligothiophene was used as the donor unit. Dodecyl group were also introduced into the thiophene moiety to explore the side chain effect on the properties of these copolymers. The optimum direct arylation reaction conditions were explored in order to obtain high molecular weight regular D–A1–D–A2 copolymer. It is found that the dodecyl group on thiophene moiety can improve the coplanarity and conjugation along the main chain of D–A1–D–A2 copolymer. These copolymers exhibit a broad absorption, narrow band gap and high packing order. Such properties are helpful for improving the photovoltaic properties. The relationship between the molecular weight and the photovoltaic property in copolymer P1 was also revealed. As the result, a higher power conversion efficiency of 3.65% was achieved for the copolymer P1 with a molecular weight of 86.1 kDa.

Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by -OCH3, -CH3 -COOCH3 and -CN, respectively. The polycondensations via direct arylation took place between the four thiophene derivatives and 2,7-dibromo-9,9-dioctylfluorene under six various catalytic conditions to investigate the substituent effects. The substituent can affect the electron cloud density of the active C-H bond, which can be monitored by the NMR chemical shift. The experimental results show that the reactivity decreases with increasing the chemical shift of active C-H bonds in the four thiophene derivatives, and thus can promote the direct arylation polycondensation. This phenomenon is explained by the electrophilic aromatic substitution (SEAr) mechanism. UV-Visible absorption and photoluminescence were studied to investigate the substituent effect on optical properties of the four copolymers. The results show that these alternating fluorene-thiophene copolymers with different substituents are good fluorescent materials and promising in PLED applications.

Poly(ether ether ketone) (PEEK) containing methyl groups was synthesized by the aromatic nucleophilic polycondensation reaction of 4, 4′-difluorobenzophenone, bisphenol-A and 2, 3,5-trimethylhydroquinone. Side-chain-type ion exchange membranes based on PEEK-g- P(DMAEMA) (poly(2-dimethylamino ethyl methacrylate)) were successfully synthesized via atom transfer radical polymerization (ATRP), using bromethylated poly(ether ether ketone) (BMPEEK) as the macroinitiator. These copolymers contain tertiary amino groups on their side chains with high molecular weight. The copolymer membranes exhibit excellent mechanical properties due to their aromatic backbone structure and flexible DMAEMA aliphatic chains. With the increase of grafting degree of DMAEMA, the ion exchange capacity (IEC) and water content of the membranes increase from 2.17 to 2.49 mmol · g−1 and 67.22 to 90.97 %, respectively. The bipolar membranes originated from PEEK-g-P(DMAEMA) display reasonably high OH− permeability and low AC impedance with high IEC.

A low-cost, hyper-branched, carbazole-based polymer (HB-Cz) was designed and synthesized by a facile “A3 + B2” one-pot Suzuki polycondensation reaction. Due to the hyper-branched structure and carbazole unit, HB-Cz is a promising candidate for a hole-transporting material, which was confirmed in perovskite solar cells (PVSCs) with a configuration of ITO/TiO2/MAPbI3/HB-Cz/Ag. The films of poly-(3-hexylthiophene) and linear poly[N-(1-octylnonyl)-9H-carbazole-2,7-diyl] were also used as hole-transporting layers (HTLs) in the reference devices. Time-resolved photoluminescence spectra indicate that HB-Cz has the fastest charge regeneration. Electrochemical impedance spectroscopy revealed that HB-Cz could reduce carrier recombination effectively, improving the open circuit voltage and fill factor of the PVSCs. A PCE of 14.07% obtained from the HB-Cz-based device was much higher than those of devices based on P3HT (9.05%) and PCz (6.60%), and this is attributed to the superior hole-transporting property and surface smoothing effect of the HB-Cz HTL.

Full-solution processed, flexible, top-emitting polymer light-emitting diodes (PLEDs) are fabricated by using low-cost and high-quality printed Ag electrodes. Employing a composite cathode (Ag/ZnO/PEI) and bi-layer anode of WO3/PH1000, the resulting devices exhibit quite comparable device performances to the conventional PLEDs, remarkable flexibility and great potential for large-area production.

The non-emissive benzene ring and green-emissive arylmaleimide are employed as two independent cores to construct dual-core white star-shaped polymers (DC-PFMs). Due to the totally star-shaped structure, DC-PFMs display a higher quantum yield and electroluminescence efficiency for a more efficient energy transfer from the host to the guest than traditional single-core polymers (SC-PFMs).

A novel Λ-shaped donor–π–acceptor–π–donor molecule BCPMM with AIEE, CIEE and polymorphism-dependent fluorescence properties was developed. The emission of BCPMM in solid states could be tuned by an external stimulus, which was utilized to construct five simple logic gates and more than ten kinds of sequential combinational logic systems.

A series of benzamide-based diphenyl maleimide derivatives 2a–d with strong crystallization-induced emission (CIE) activity were synthesized and investigated. 2a–d are almost non-emissive in solutions and amorphous films, but intensely and greenly emissive in crystalline powders and crystals with a quantum yield of 53% and 80%, respectively. The results of X-ray diffraction analysis and theoretical calculation demonstrate that the intramolecular hydrogen bond between CO and NH groups formed in the excited state of 2 quenches the fluorescence, resulting from the rotation of benzamide groups in their solution and amorphous states. However, it would not happen in their crystalline sates for the locked conformation. Thus, the formation and inhibition of the hydrogen bonding in the excited state may be responsible for their CIE activity. Interestingly, the florescence of the 2d solid can be switched between on/off states by external stimuli including grind, heat, solvent vapor, and acid/alkali, which was utilized to develop three kinds of new technologies for rewritable information storage and security ink.