Improving the Efficiency and Stability of MAPbI Perovskite Solar Cells by Dipeptide Molecules.

Passivating the electronic defects of metal halide perovskite is regarded as an effective way to improve the power conversion efficiency (PCE) of perovskite solar cells (PVSCs). Here, a series of dipeptide molecules with abundant ─C═O, ─O─ and ─NH functional groups as defects passivators for perovskite films are employed. These dipeptide molecules are utilized to treat the surface of prototype methyl ammonium lead iodide (MAPbI) films and the corresponding PVSCs exhibit enhanced photovoltaic performance and ambient stability, which can be ascribed to: 1) the ─C═O and ─O─ can interact with the undercoordinated Pb ions and the ─NH groups can form hydrogen bonds with the I ions, passivating the defects in perovskite film and reducing charge recombination in PVSCs; 2) the long alkyl chain of dipeptide molecules increases the hydrophobicity of the perovskite surface and thus enhance the stability of PVSCs.

Enhanced Self-Assembly of Crystalline, Large-Area, and Periodicity-Tunable TiO Nanotube Arrays on Various Substrates.

Due to their superior physical properties, titanium dioxide (TiO) nanotube arrays are one of the most investigated nanostructure systems in materials science until now. However, it is still a great challenge to achieve damage-free techniques to realize controllable, cost-effective, and high-performance TiO nanotube arrays on both rigid and flexible substrates for different technological applications. In this work, we demonstrate a unique strategy to achieve self-assemble crystalline, large-area, and regular TiO nanotube arrays on various substrates via hybrid combination of conventional semiconductor processes.

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices.

Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy.

Decomposition of Organometal Halide Perovskite Films on Zinc Oxide Nanoparticles.

Solution processed zinc oxide (ZnO) nanoparticles (NPs) with excellent electron transport properties and a low-temperature process is a viable candidate to replace titanium dioxide (TiO2) as electron transport layer to develop high-efficiency perovskite solar cells on flexible substrates. However, the number of reported high-performance perovskite solar cells using ZnO-NPs is still limited. Here we report a detailed investigation on the chemistry and crystal growth of CH3NH3PbI3 perovskite on ZnO-NP thin films.

Controllable Synthesis of Bandgap-Tunable CuSx Se(1-x) Nanoplate Alloys.

Composition engineering is an important approach for modulating the physical properties of alloyed semiconductors. In this work, ternary CuS(x)Se(1-x) nanoplates over the entire composition range of 0≤x≤1 have been controllably synthesized by means of a simple aqueous solution method at low temperature (90 °C). Reaction of Cu(2+) cations with polysulfide/-selenide ((S(n)Se(m))(2-)) anions rather than independent S(n)(2-) and Se(m)(2-) anions is responsible for the low-temperature and rapid synthesis of CuS(x)Se(1-x) alloys, and leads to higher S/Se ratios in the alloys than that in reactants owing to different dissociation energies of the Se-Se and the S-S bonds.

Energy-band engineering for tunable memory characteristics through controlled doping of reduced graphene oxide.

Tunable memory characteristics are used in multioperational mode circuits where memory cells with various functionalities are needed in one combined device. It is always a challenge to obtain control over threshold voltage for multimode operation. On this regard, we use a strategy of shifting the work function of reduced graphene oxide (rGO) in a controlled manner through doping gold chloride (AuCl3) and obtained a gradient increase of rGO work function.

A versatile triphenylamine/fluoranthene-based derivative as a nondoped green-emitting, hole-transporting interlayer for electroluminescent devices.

A new triphenylamine-bridged fluoranthene derivative, 4-(7,10-diphenylfluoranthen-8-yl)-N-[4-(7,10-diphenylfluoranthen-8-yl)phenyl]-N-phenylaniline (BDPFPA), with a high glass transition temperature of 220 °C has been synthesized and characterized. BDPFPA is a highly fluorescent and versatile material that can be used as a nondoped green emitter and as a hole transporter. BDPFPA was used in a standard trilayer device as the emitting layer, which showed a low turn-on voltage (<3 V) and a high efficiency of 11.

Highly active and enhanced photocatalytic silicon nanowire arrays.

Nanoporous and nonporous three-dimensional silicon nanowire arrays (SiNWAs) prepared with metal-assisted chemical etching method were investigated as photocatalysts in dye photodegradation systematically. In comparison with nonporous SiNWAs, nanoporous SiNWAs have higher surface area, larger pore volume, stronger light absorption and better photocatalytic activity. After the HF-treatment, the photocatalytic activity of all kinds of SiNWAs increased significantly and the nanoporous SiNWAs showed excellent stability.

[Studies on the chemical constituents of Lithocarpus polystachyus].

Objective: To study the chemical constituents from Lithocarpus polystachyus.

Methods: Compounds were isolated and purified with silica gel, and there structures were identified by chemical property and spectral data.

Results: Nine compounds were isolated as phloridzin (I), phloretin (II), dihydrochalcone-2'-beta-D-glucopyranoside (III), daucossterol (IV), beta-sitosterol (V), quercetin (VI), luteolin (VII), quercitrin (VI), oleanolic acid (IX).