Here we demonstrate a simple and effective method of fabricating polymeric scattering substrate for flexible organic light-emitting diodes (OLEDs) that require no costly patterning, etching, or molding processes, aspects that are desirable for the commercialization of large-scale lighting panels. Systematic study of the influences of relative index of refraction, particle size, and doping concentration on transmittance and haze of transparent colorless polyimide (cPI) films was carried out. It was found that the reduction of transmittance and haze of the doped films decreases along with the decrease of the difference of refractive index between the particles and polymer matrix, and it could be compensated by the increase of particle size or doping concentration.Keywords: colorless polyimide; flexible; haze; nanoparticle; scattering;

An interface stabilizer based on alkylation-functionalized fullerene derivatives, [6, 6]-Phenyl-C61-butyric acid (3,5-bis(octyloxy)phenyl)methyl ester (PCB-C8oc), was successfully synthesized and applied for the active layer of Organic Photovoltaics (OPVs). The PCB-C8oc can replace part of the phenyl-C61-buty-ric acid methyl ester (PCBM) and be distributed on the interface of poly(3-hexylthiophene) (P3HT) and PCBM to form P3HT/PCBM/PCB-C8oc ternary blends, leading to thermally stable and efficient organic photovoltaics. The octyl groups of PCB-C8oc exhibit intermolecular interaction with the hexyl groups of P3HT, and the fullerene unit of PCB-C8oc are in tight contact with PCBM. The dual functions of PCB-C8oc will inhibit the phase separation between electron donor and acceptor, thereby improving the stability of devices under long-time thermal annealing at high temperature. When doped with 10 wt % PCB-C8oc, the power conversion efficiency (PCE) of the P3HT system decreased from 3.54% to 2.88% after 48 h of thermal treatment at 150 °C, whereas the PCE of the reference device without PCB-C8oc dramatically dropped from 3.53% to 0.73%. When doping 10 or 20 wt % PCB-C8oc, the unannealed P3HT/PCBM/PCB-C8oc device achieved a higher PCE than the P3HT/PCBM device without any annealing following the same fabricating condition. For the PTB7/PCBM-based devices, after adding only 5 wt % PCB-C8oc, the OPVs also exhibited thermally stable morphology and better device performances. All these results demonstrate that the utilization of alkyl interchain interactions is an effective and practical strategy to control morphological evolution.Keywords: aggregation; alkylation-functionalized; interface stabilizer; morphological evolution; organic photovoltaics; thermal stability;

•Chlorine-bearing conjugated polymers exhibit unique properties.•Revealing the structure-property relationship of chlorine-bearing polymers.•Efficient deep-red electroluminescent materials.Since the large steric hindrance caused by chlorine atoms not only suppresses the aggregation but also results in large stokes shift and low self-absorption, a series of donor-acceptor alternating copolymers based on 6,7-dichloroquinoxaline have been synthesized by modifying the structures of oligothiophenes. All the polymers have been well characterized to study the effects of the length of oligothiophenes and the steric hindrance on the optical, electronic and electroluminescent properties. It was observed that the intramolecular charge transfer absorption was weakened by steric hindrance. Unlike non-chloride analogues, prolonged conjugated length resulted in smaller bandgap, given similar steric hindrance. Deep-red emission centered at 678 nm with brightness about 1800 cd m−2 was achieved with external quantum efficiency 1.34% using dopant/host technic.Download high-res image (291KB)Download full-size image

Efficient indium tin oxide (ITO)-free inverted polymer solar cells (PSCs) were fabricated by applying ultrathin metal transparent electrodes as sunlight incident electrodes. Smooth and continuous Ag film of 4 nm thickness was developed through the introduction of a 2 nm Au seed layer. Ultrathin Ag transparent electrode with an average transmittance of up to 80% from 480 to 680 nm and a sheet resistance of 35.4 Ω/sq was obtained through the introduction of a ZnO anti-reflective layer. The ultrathin metal electrode could be directly used as cathode in polymer solar cells without oxygen plasma treatment. ITO-free inverted PSCs obtained a power conversion efficiency (PCE) of 5.2% by utilizing the ultrathin metal transparent electrodes. These results demonstrated a simple method of fabricating ITO-free inverted PSCs.

•A series of thermally durable (Tg > 320 °C) isomeric polyimides with a rigid alicyclic structure were prepared.•An ultra-thin transparent flexible MoO3(3 nm)/Au(2 nm)/Ag(4 nm) electrode was deposited ontop of the polyimide substrates.•Flexible QLED and OPV devices exhibited good devices efficiencies.A series of isomeric alicyclic-functionalized polyimide with chemical imidization and thermal imidization (CPI-x and TPI-x) were prepared from a rigid alicyclic-functionalized isomerism diamine, 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (DAPI). The influences of incorporation of the isomeric rigid alicyclic structure onto the backbone of the polymers were systematically investigated in terms of optical, thermal, mechanical, dielectric and surface properties, respectively. Due to the moderate chemical imidization condition, CPI-x series retain higher glass transition temperature (Tg) in the range of 329–429 °C than the Tg of TPI-x (from 321.9 °C to 370.7 °C). Therefore, the CPI-1 film based 5-DAPI was chosen as the flexible substrate. MoO3 was chosen as the interface layer to improve the compatibility between PI substrate and the metal electrode. Then a ultra-thin layer of MoO3 (3 nm)/Au(2 nm)/Ag(4 nm) was utilized to be the transparent electrode. After annealing at 220 °C for 0.5 h, zinc oxide (ZnO) was deposited onto the electrode to maintain the superior electron mobility and improve the transparency of the electrode. Consequently, the flexible quantum dots light emitting diode (QLED) obtained a high luminance of 5230 (cd/m2) and EQE of 5.2%, meanwhile, a device performance of 4.36% was achieved in organic photovoltaic (OPV) devices.The rigid alicyclic asymmetric isomer influences the properties of transparent polyimide substrates for flexible QLED and OPV devices.Download high-res image (183KB)Download full-size image

A zinc complex host material named Zn(PPI)2 (PPI = 2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol) is synthesized by an improved strategy. Combined with dopant Ir(piq)3 and Ir(pmiq)2(acac), deep-red phosphorescent organic light-emitting diodes are fabricated and investigated. The devices show a highest external quantum efficiency of 9.5% based on Ir(piq)3 and 13.1% for Ir(pmiq)2(acac). All these devices show very stable electroluminescent spectra without significant shift during current density increase. Commission Internationale de l'Eclairage coordinates of (0.68, 0.32) and (0.70, 0.30) are obtained respectively.

High selectivity and yield of aryl–aryl coupling reactions between chlorine-containing aromatic bromides and organotin reagents are reported. The variable reaction selectivity between bromine and chlorine mainly depends on the electronic effects of the aromatic substrates. The reactivity of chlorine can be completely restrained by employing the optimized palladium catalysts, which can be used for the preparation of chlorine-bearing molecules. Then, a series of high molecular weight conjugated copolymers with chlorine on the backbones are straightforwardly synthesized by the Stille condensation reaction. The chlorine-bearing polymers exhibit much lower LUMO, larger Stokes shift and less self-absorption compared with the non-chlorine analogues because of the electron affinity and the large steric hindrance of chlorine atoms. Efficient NIR emission centred at about 758 nm can be obtained based on the single layer system.

•High molecular weight and non-crosslinking chlorine-bearing polymers have been straight forward synthesized.•Chlorine-bearing polymers exhibit lower LUMO, larger Stokes shift and lower self-absorption.•These polymers bearing chlorine atoms on the backbone can be used as efficient light-emitting materials.High molecular weight and non-crosslinking conjugated donor–acceptor copolymers with chlorine on the backbones were straight forward synthesized for the first time under Stille condensation reaction by using the different reaction activities between chlorine and bromine atoms. The chlorine-bearing polymers exhibited much lower LUMO, larger Stokes shift and lower self-absorption compared with the non-chloride analogue, for the electron affinity and large steric hindrance of chlorine atoms. Deep red to NIR emission centered at 698 nm was obtained with brightness about 1500 cd/m2 and centered at 708 nm was obtained with brightness over 400 cd/m2 based on dopant/host system.Graphical abstract

High selectivity and yield of aryl–aryl coupling reactions between chlorine-containing aromatic bromides and organotin reagents are reported. The variable reaction selectivity between bromine and chlorine mainly depends on the electronic effects of the aromatic substrates. The reactivity of chlorine can be completely restrained by employing the optimized palladium catalysts, which can be used for the preparation of chlorine-bearing molecules. Then, a series of high molecular weight conjugated copolymers with chlorine on the backbones are straightforwardly synthesized by the Stille condensation reaction. The chlorine-bearing polymers exhibit much lower LUMO, larger Stokes shift and less self-absorption compared with the non-chlorine analogues because of the electron affinity and the large steric hindrance of chlorine atoms. Efficient NIR emission centred at about 758 nm can be obtained based on the single layer system.