Perovskite solar cells (PVSCs) have recently gained much attention for the advantages of low cost and high efficiency. Based on the different device structures, PVSCs can be simply classified into conventional and inverted categories. Compared with the inverted devices, conventional PVSCs generally exhibited higher PCE. Especially, a milestone PCE value of 24.3% was obtained in conventional PVSCs. However, the complexity and high-temperature process in device fabrication further limit their application in flexible and large-scale devices, while the inverted PVSCs can make up the shortcomings of the conventional PVSCs. Commonly, PVSCs devices contain electrodes, electron/hole transporting layers and the perovskite layer. Among the function layers, hole transporting layers (HTLs) play a crucial role in improving the photovoltaic performance of inverted PVSCs. From the materials point of view, the efficient hole transporting materials (HTMs) are mostly inorganic compounds and polymers. On the other side, taking advantages of easy modification, low price, easy preparation and homogeneity in batches, small molecular HTMs afford superior promising in fabricating efficient and stable PVSCs. However, up to date, small molecular HTMs are relatively less explored. To enrich the material species of small molecular HTMs and illustrate their superiorities in constructing stable PVSCs, in this paper, we designed and synthesized three D-π-A-π-D type small molecular HTMs based on triphenylamine (TPA) unit, namely 1-T, 1-OT and 1-OTCN. The optoelectronic properties of these molecules were modified by introducing different electron acceptor/donor groups. Afterwards, employing as dopant-free HTMs in inverted PVSCs, the three small molecules demonstrated distinguished performance. We found that introduction of electron-donating methoxy into 1-T, 1-OT exhibited increased energy levels and hole mobility. On the other

The effect of hydrofluoric acid （HF） etching time on Ni/6H-SiC ohmic contacts was investigated． The as-deposited Ni/6H-SiC contacts prepared by 6H-SiC substrates which have been subjected to different HF etching time have different I-V characteristics． For SiC substrates etched for less than 12 hours, the contacts were rectifying, and excellent linear curves were observed after high temperature thermal annealing．X_ray diffraction, Auger electronic spectroscopy and low_energy reflection electron energy loss spectroscopy showed that Ni2Si and amorphous C were the main reaction products after annealing.For SiC substrate etched for 24 hours, the as-deposited Ni/6H-SiC contact was ohmic． The carbon-enriched layer （CEL） on the SiC surface plays an important role in the formation of ohmic contact．

Organic-inorganic hybrid perovskite is a class of direct-bandgap semiconductors that can be processed as thin films from solutions by low-temperature methods. Among various solution-processable semiconductor materials, the hybrid perovskites exhibit unique combination of low bulk-trap densities, remarkable ambipolar transport properties, good broadband absorption characteristics and long charge carrier diffusion lengths, making them ideal for photovoltaic applications. Furthermore, as direct bandgap semiconductors with low bulk trap densities, the hybrid perovskite films possess remarkable luminescent properties. The bandgap of the hybrid perovskites can be tuned by crystal engineering, i.e. tuning the composition at molecular levels. These intriguing properties indicate that the hybrid perovskites may also find applications in light-emitting diodes and lasing. This paper reviews the unique properties and current research progresses of this class of dream material and provides our perspective of future directions.

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