Effective hot-air annealing for improving the performance of perovskite solar cells

Abstract

We report a simple and effective method for improving the performance of CH3NH3PbI3-xClx perovskite solar cells. By employing a moisture pretreatment (MPT) and,a novel hot-air annealing process (HAAP) for preparing the perovskite CH3NH3PbI3-xClx film, we could successfully enhance the crystallinity of the CH3NH3PbI3-xClx active layer and improve its photon collection properties. This led to a marked improvement in device performance. Solar cells with the structure indium tin oxide/poly(3,4-ethylenedioxythio phene) -poly(styrenesulfonate)/CH3NH3PbI3-xClx active layer/[6,6]-phenyl-C61-butyric acid methyl ester/Ca/Al and fabricated using the MPT process and the HAAP method showed significantly improved performance, including higher power conversion efficiency (PCE) and fill factor values than those of the device fabricated conventionally. The PCE increased from 9.05 to 11.87% when the MPT process was used and from 9.05 to 15.55% when both MPT and HAAP were used. Moreover, the HAAP device did not exhibit photocurrent hysteresis, which is always observed in the case of the conventionally fabricated solar cells owing to the charge traps resulting from the low quality of the perovskite film. (C) 2017 Elsevier Ltd. All rights reserved.