Elucidating the evolution of the current-voltage characteristics of planar organometal halide perovskite solar cells to an S-shape at low temperature

The temperature dependence of initial transient current-voltage (I-V) characteristic of planar perovskite solar cell by one-step solution process is investigated. An S-shaped I-V characteristic emerges in response to low temperature and the photovoltaic parameters drop dramatically. This is mainly attributed to the increasing amount of negative charges accumulating in the TiO2/CH3NH3PbI3 interface region and the reduced built-in field separating the photo-generated carriers in the absorber layer. The influence of negative charge accumulation can be represented by two extra diodes that are in series with a conventional solar cell circuit model at low temperature whereas it acts as a resistor with low resistivity above room temperature. These findings help to understand the charge transport mechanism in perovskite solar cells. (C) 2016 Elsevier B.V. All rights reserved.