Stability Improvement and Performance Reproducibility Enhancement of Perovskite Solar Cells Following (FA/MA/Cs)PbI3–xBrx/(CH₃)₃SPbI₃ Dimensionality Engineering

Mixed halide hybrid perovskites are strong candidates for fabrication of efficient, stable and reproducible perovskite solar cells (PSCs). To restrain intrinsic volatility and ionic migration effects, we report for the first time a dimensionality engineering approach consisting of a (FA/MA/Cs)PbI 3– x Br x /(CH 3 ) 3 SPbI 3 (3D/1D) perovskite bilayer architecture, fabricated exclusively with solution processes. XRPD analysis showed no degradation of the 3D/1D composite structure after more than one month of exposure in ambient conditions, in contrast to the reference 3D samples (sole (FA/MA/Cs)PbI 3– x Br x ) which gradually decomposed to PbI 2 . The 3D/1D bilayer structure further optimizes the corresponding absorber/hole transporting layer (HTL) interface of the PSCs, since the (FA/MA/Cs)PbI 3– x Br x perovskite layer acts as the primary absorber and the (CH 3 ) 3 SPbI 3 top layer plays the role of a barrier against ionic migration/charge carrier recombination. The latter leads to a significant stability improvement for nonsealed devices both under ambient conditions and light stress, underscoring the potential of interface engineering for developing highly efficient and stable PSCs based on functional 3D/1D perovskite bilayers.