We have prepared perovskite [CH 3 NH 3 PbI 3 (MALI), CH 3 NH 3 PbBr 3 (MALB), NH 2 CH=NH 2 PbI 3 (FALI), and NH 2 CH=NH 2 PbBr 3 (FALB)] thin films by a one-step process on glass/TiO 2 and glass/Al 2 O 3 substrates and studied the stability of the perovskite under UV/visible light radiation up to 24 h at 1.5AM in air. After irradiation, the films were characterized by UV-vis absorption and X-ray diffraction measurements. In addition, photovoltaic performance characteristics in air were studied using different perovskites before (0 h) and after 24 h irradiation. The results revealed that Al 2 O 3 protected the perovskite crystal from degradation. However, the perovskites were unstable except for NH 2 CH=NH 2 PbI 3 under the same conditions using a TiO 2 scaffold layer.

In order to analyze the crystal transformation from hexagonal PbI2 to CH3NH3PbI3 by the sequential (two-step) deposition process, perovskite CH3NH3PbI3 layers were deposited on flat and/or porous TiO2 layers. Although the narrower pores using small nanoparticles prohibited the effective transformation, the porous-TiO2 matrix was able to help the crystal transformation of PbI2 to CH3NH3PbI3 by sequential two-step deposition. The resulting PbI2 crystals in porous TiO2 electrodes did not deteriorate the photovoltaic effects. Moreover, it is confirmed that the porous TiO2 electrode had served the function of prohibiting short circuits between working and counter electrodes in perovskite solar cells.

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The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 film prepared at low temperature using different solvents was investigated.SnO2 was selected as an electron conducting medium due to its superior properties over TiO2, such as better antireflective properties, higher electron mobility, more suitable band edges and a wider band gap. A SnO2 layer was developed by spin-coating SnCl2 solution followed by annealing at 200°C in air. The low-temperature (200 °C) annealed SnO2 layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology using ethanol as a solvent rather than water. Solid state CuSCN hole conductor was used as HTM for reducing the device cost. A planar solar cell fabricated with CH3NH3PbI3 perovskite infiltrated SnO2 showed a power conversion efficiency of 8.38% with short-circuit current density of 18.99 mA/cm 2 , an open-circuit voltage of 0.96 mV and a fill factor of 45%. The devices were fabricated at >60% humidity level at room temperature. The results suggest that SnO2 is an effective charge collection system for CH3NH3PbI3 based planar perovskite solar cells. In addition, these results © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 provide a new direction for the future improvement of perovskite solar cells using new electron conducting layers.