Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)
Publication date: 28th March 2016
Perovskite solar cells have received grate attention for their high performance recently. It has been proved that surface coverage, crystal size and film roughness of perovskite are crucial parameter for improving the cell performance. In particular, in order to improve perovskite film properties, many fabrication methods were conducted such as DMSO-assisted, H2O-assisted, thermally induced and acid treated crystallization methods. Herein, perovskite solar cells were fabricated with the thermally induced crystallization method by varying the temperature systematically 0, 20, 40 and 60 ℃ and yielded the overall energy conversion efficiency of 12, 12.2, 13.1 and 11%, respectively. Thus, electron transport properties such as free carrier lifetime, charge transport resistance in perovskite layers were characterized by intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectroscopy (EIS). It was found that the crystal size and the surface coverage of perovskite were directly influenced by changing the thermal treatment condition, which in turn affect electron transport phenomena. At higher temperatures, the size of the perovskite crystal became bigger but the surface coverage was poorer, but the low temperature-treated perovskite showed smaller size but higher surface coverage. When the crystal size is large, light scattering can improve light absorption but the low surface coverage can make a room for direct contact between the electron transport layer and the hole transport layer, accelerating electron back transport and shorten electron lifetime. Therefore it was concluded that the crystal size of perovskite should be optimized to maximize the overall energy conversion efficiency.