Defect control for high-efficiency all-inorganic CsPbBr3 perovskite solar cells via hydrophobic polymer interface passivation

Abstract

All-inorganic CsPbBr3-based perovskite solar cells (PSCs) have been proved to possess upgraded humidity and thermal stability. However, the CsPbBr3-based PSCs with a typical device configuration without hole transport layer (HTL) suffer from serious carrier recombination as a result of high interfacial defect density, which limits the enhancement of photoelectric conversion efficiency (PCE). To settle this issue, an interfacial engineering methodology is imported by utilizing polymethyl methacrylate (PMMA) as a passivation layer between the CsPbBr3 film and the carbon electrode. Through the interaction within the uncoordinated Pb2+ ions and oxygen atoms of carbonyl (CO) in the PMMA molecule chains, the trap sites existed in the modified CsPbBr3 interface can be greatly suppressed, beneficial for a faster extraction and transportation of photogenerated carriers. Besides, the PMMA interlayer can raise the valence band of the CsPbBr3 surface for a better energy level alignment, and simultaneously portray as a protective layer against moisture owing to the hydrophobic nature of long-chain polymers. Ultimately, the PMMA modified device exhibited a champion PCE of 9.60 % with a high open-circuit voltage (VOC) of 1.58 V, as well as showcasing ignorable PCE loss enduring over 400 h of aging.