Flexible Perovskite Solar Cells onto Plastic Substrate Exceeding 13% Efficiency Owing to the Optimization of CH₃NH₃PbI_3–<i>x</i>Cl_<i>x</i> 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/CH 3 NH 3 PbI 3– x Cl x /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 H 2 O additive into the perovskite precursor solution leads to an enhanced CH 3 NH 3 PbI 3– x Cl x perovskite quality for F-PSCs application, including the improvement of morphology and electrical properties. To better summarize the mechanism concerning how H 2 O additive affects the perovskite film quality, CH 3 NH 3 PbI 3– x Cl x films are prepared by a simple one-step spinning method from a solution containing CH 3 NH 3 I, PbI 2, and PbCl 2 in a mixed solvent of H 2 O and dimethylformamide (DMF) with solely various volume ratio ranging from 0.1% to 0.9%. Through a comparative analysis, it is proposed that H 2 O additive prolongs the CH 3 NH 3 PbI 3– x Cl x 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.