The rich molecular design of electron donor (D)–acceptor (A) polymers offers many valuable clues to obtain high‐efficiency hole‐transporting materials (HTMs) for use in perovskite solar cells (PVSCs). The fused aromatic or heteroaromatic units can increase the conjugation of the polymer backbone to facilitate electron delocalization, which increases the rigidity of adjacent units to prevent rotational disorder and lower the reorganization energy, leading to improved carrier mobility and optimized film morphology. In this work, fused‐ring ladder‐type indacenodithiophene and indacenodithieno[3,2‐b]thiophene are used as D units, benzodithiophene‐4,8‐dione as the A unit, and thienothiophene as a π‐bridge to form the D–A polymers PBDTT and PBTTT, respectively. Both polymers exhibit favorable properties as HTMs including suitable energy levels, high hole mobility, and excellent film quality. Both dopant‐free HTMs endow n‐i‐p PVSCs with promising performance and stability. A maximum power conversion efficiency of 20.28% is achieved for PBDTT‐based devices, which is among the highest values reported to date.

A novel hyper-branched carbazole-based polymer is synthesized and used as hole-transporting material for PVSCs giving a PCE of 14.07%.

Perylene diimide‐based small molecules are widely used as intermediates of liquid crystals, owing to their high planarity and electron mobility. In this study, tetrachloroperylene diimide (TCl‐PDI) was used as a small‐molecule replacement for TiO2 as electron‐transporting material (ETM) for planar perovskite solar cells (PVSCs). Among hole‐transporting materials (HTMs) for PVSCs, poly(3‐hexylthiophene) (P3HT) gives the devices the highest stability and reproducibility. Therefore, PVSCs with the structure of indium tin oxide (ITO)/ETM/perovskite/P3HT/MoO3/Ag were used to evaluate the performances of new ETMs. A reference device with compact TiO2 and P3HT gave a reasonable power conversion efficiency (PCE) of 12.78 %, whereas the PVSC with TCl‐PDI as ETM gave an enhanced PCE of 14.73 %, which is among the highest reported values for PVSCs with undoped P3HT as the HTM. Moreover, TCl‐PDI‐based devices displayed higher stability than those based on compact TiO2, owing to the superior perovskite quality.

Top-emitting microcavity polymer light-emitting diodes (TMPLEDs) are of great significance for active matrix PLED displays with high color purity. However, the complex device structures of highly efficient microcavity organic light-emitting diodes fabricated by the full vapor deposition technology are not suitable for solution-processed PLEDs. Solution-processed TMPLEDs with simple device structures are promising candidates for large-area, mass production display techniques. In this work, three strategies were used to apply microcavity into PLEDs: (1) double Ag electrodes performed as the mirrors of cavity, instead of a multi-layer Bragg reflector, which simplified the device structure and fabrication process; (2) three solution-processed functional layers were specially designed for avoiding the inter-infiltration between the different solutions and to improve the interface contacts; (3) high order microcavities were utilized according to the optical simulation results, in which thick EMLs benefited from thickness control and reproductivity. As a result, the full-color emission including pure red, green, blue was realized, and quasi-white light was also achieved from a single polymer emitting material. The achievement of color purity always requires the sacrifice of part of the current efficiency due to the spectra narrowing, while the higher current efficiency of green TMPLED (10.08 cd A−1) compared to that of non-cavity PLED (~8.60 cd A−1) cast a light on future improvements.

No abstract

Interface engineering of TiO2 nanoparticles (NPs)‐based perovskite solar cells (PVSCs) is often necessary to facilitate the extraction and transport of charge carriers. In this work, poly[{9,9‐bis[3′‐(N,N‐dimethyl)propyl]‐2,7‐fluorene}‐alt‐2,7‐(9,9‐dioctylfluorene)] (PFN) and polystyrene (PS) are demonstrated to be effective surface modifiers of the TiO2 NPs electron‐transporting layer in n‐i‐p PVSCs. The low‐cost insulating polymer PS performs better than the PFN conjugated polymer owing to its high film quality, low surface energy and insulating characteristics. A peak power conversion efficiency (PCE) of 15.09 % with an open‐circuit voltage (VOC) of 1.05 V and a PCE of 17.13 % with an ultrahigh VOC of 1.18 V is achieved with TiO2 NPs/PS‐based PVSCs using poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) and spiro‐OMeTAD, respectively, as the hole‐transporting material.

No abstract