Origin of thermal instability of CH3NH3PbI3-xClx films for photovoltaic devices

The rapid improvements in perovskite solar cells have led to high power conversion efficiencies of over 20% in recent years. Despite this remarkable performance, the mechanism of thermal instability for those films is still one of the problems that we have to face. In this work, we systematically measure the thermal stability of CH(3)NH(3)Pbl(3-x)Cl(x) films on substrates of ITO, PEDOT:PSS/ITO, TiO2/ITO, at various temperatures. Comparing their counterparts on Glass, PEDOT:PSS/Glass, TiO2/Glass, we found that the films on substrates with ITO are always less thermal stable, resulting from charge transfer between perovskite and ITO substrates, in particular at higher annealing temperatures. Therefore, it was believed that more thermal degradation can occur in CH(3)NH(3)Pbl(3-x)Cl(x) film with less neutral electrical environment. (C) 2016 Elsevier B.V. All rights reserved.