Recently, inverted planar heterojunction (PHJ) perovskite solar cells have been developed rapidly by numerous preparations and relative optimizations. Sequential solution deposition is easy to manipulate but it is difficult to control the thickness and morphology of perovskite films. In this article, we report an improved sequential deposition, named twice dipping-vapor solution deposition (TD-VSD) technology, to accurately achieve superior perovskite films. It is demonstrated that the morphology of perovskite films depended on the substrate temperatures as well as the dipping times. The resulting solar cells showed the power conversion efficiency as high as 11.77% based on the ideal thickness and morphology. This work provides a simple but effective fabrication to well control the perovskite films and enhance the power conversion efficiency for inverted PHJ solar cells.

We manufactured polarizing polymer solar cells (PSCs) utilizing a liquid crystalline polymer (i.e., pol y(2,5-bis(3-dodecylthiophen-2-yl) thieno[3,2-b] thiophene) (PBTTT)) as an electron donor material and a material that selectively absorbs polarized light. The oriented PBTTT films prepared using a self-organization process exhibited a high dichroic ratio of ca. 6.35 at the absorption peak. The polarizing PSCs based on oriented PBTTT-PC71BM photoactive layers exhibit an anisotropic photovoltaic effect under polarized illumination along the two orthogonal axes. The polarizing PSCs have a larger power conversion efficiency under parallel-polarized illumination than that of isotropic PV devices under unpolarized illumination. Based on picosecond fluorescent spectra, the parallel excitation produces a slower ground state recovery and a longer exciton lifetime than perpendicular excitation for PBTTT molecules in a uniaxially oriented arrangement. (C) 2015 Elsevier B.V. All rights reserved.

In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) or 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is similar to 1.7 mu m for electrons and up to similar to 6.3 mu m for holes. Short diffusion distance of few hundreds of nanosecond was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (similar to 100 nm) in films and resolved its confliction to thick working layer (300-500 nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices' design.

In this study, mesoscopic optical structured 2,9-dimethyl-4,7-diphenyl-1,10-phenyl-1,10-phenanthrolin (bathocuproine, BCP) film was formed to enhance the out-coupling efficiency of a top blue organic light-emitting device (OLED). Based on the refractive index matching layer of BCP on the electrode, the light can be extracted through waveguide mode. Owing to the low glass transition temperature (T-g) of BCP, which easily self-aggregates in a specific environment (controlled temperature and humidity), a mesoscopic optical structure was obtained in 3 h after film formation. Through the nano-aggregated structure, the surface plasmon polariton (SPP) mode can match the free optic field. The efficiency of the device was enhanced: the max brightness increased from 4500 to 9840 cd.m(-2) and the external quantum efficiency (EQE) increased from 0.42% to 1.14%. This leads to a 2.7-fold enhancement of top emission devices. Moreover, the EL spectra of the devices are also optimized by a blue-shift of 12 nm.

In this work, we have provided a new possible explanation for the micromechanism of electroplex. The time-resolved electroluminescent spectra of light-emitting diodes based on the blend of TAPC and TpPyPB were measured. They show that when a high bias voltage is applied on the devices, the electroplex emission gradually increases over time. After the devices worked at a high bias voltage, a strong electroplex emission can be maintained at low bias voltage, but the peaks related to the electroplex are still insignificant in photoluminescence. These results may suggest that the electroplex is a charge-transfer complex with changed conformation caused by polaron-induced molecular aggregation under electric field in essence, though further investigation is needed. Using materials with morphology stability under an electric field, electroplex was greatly reduced, which may enlarge the consideration in designing exciplex-based organic light-emitting diodes (ExOLEDs). (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

[6,6]-Phenyl-C61-butyric acid-4'-hydroxyl-azobenzene ester (PCBAb) was synthesized and used as the acceptor in the fabrication of reversible UV-VIS response bi-state polymer solar cells (PSCs) based on the photoinduced cis-trans isomerization of PCBAb. The device can be switched between ``active'' and ``sleep'' by the irradiation of UV and visible light, respectively. The active device has a PCE of 2.0%. With UV irradiation, the device goes to ``sleep'' with a lowered PCE (0.4%), and simultaneously decreased J(sc), V-oc and FF, while after visible light treatment, the device is made ``active'' again. The mechanism of the bi-state process involves the different electron mobilities of the isomers. (C) 2015 Elsevier B.V. All rights reserved.