CH₃NH₃PbI₃ deposited on rubrene/pentacene bilayer by two-step method and its photovoltaic performance

Optimizing the underlayer used as an active layer in perovskite solar cells is important for improving their cell performance. We previously demonstrated the usefulness of a rubrene/pentacene bilayer as an underlayer in CH₃NH₃PbI₃ (MAPbI₃) cells prepared by alternative vapor deposition of PbI₂ and CH₃NH₃I (MAI). In the present work, to examine the applicability of this rubrene/pentacene bilayer for the deposition of MAPbI₃ via a new method involving immersing a PbI₂ evaporated film into an MAI solution is used to prepare MAPbI₃ films; this method is referred to as a two-step method. Adjustment of the parameters of the two-step method used to prepare MAPbI₃ films on rubrene/pentacene bilayers led to cells with a higher power conversion efficiency compared with that of cells with MAPbI₃ films deposited directly onto poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), without rubrene/pentacene bilayers. The rubrene/pentacene presumably promotes the suppression of recombination at the interface between MAPbI₃ and the hole transport layer.