Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13% Efficiency Owing to the Optimization of CH3NH3PbI3–xClx Film via H2O Additive

Abstract

In this work, flexible perovskite solar cells (F-PSCs) are fabricated utilizing the device polyethylene terephthalate (PET) substrate/ITO/PEDOT:PSS/CH3NH3PbI3–xClx/PCBM/Ag, which exhibits the optimal power conversion efficiency (PCE) reaching 13.27%, superb stability against bending deformation, and advantageous stability in ambient atmosphere without encapsulation. Meanwhile, we herein confirm a fact that incorporating suitable H2O additive into the perovskite precursor solution leads to an enhanced CH3NH3PbI3–xClx perovskite quality for F-PSCs application, including the improvement of morphology and electrical properties. To better summarize the mechanism concerning how H2O additive affects the perovskite film quality, CH3NH3PbI3–xClx films are prepared by a simple one-step spinning method from a solution containing CH3NH3I, PbI2, and PbCl2 in a mixed solvent of H2O and dimethylformamide (DMF) with solely various volume ratio ranging from 0.1% to 0.9%. Through a comparative analysis, it is proposed that H2O additive prolongs the CH3NH3PbI3–xClx recrystallization process contributing to slower crystallization rate. Additionally, it can merge adjacent perovskite grain together by accelerating the diffusion of ions within the predeposited films toward the grain boundary, thereby yielding large and densely packed perovskite grain size.