Synergistically modifying electron transport layers and bottom buried perovskite layers of perovskite solar cells

Abstract

The electron transport layer (ETL) and its adjacent interface are essentially important for perovskite solar cells (PSCs). The commercialization of PSCs can be facilitated by coordinately regulating the ETL and the bottom buried perovskite layer through interface molecules. Here, we introduce 3-O-ethyl-L-ascorbic acid (ELAA), a derivative of vitamin C, as a co-regulator at the SnO₂/perovskite interface to suppress defects in the SnO₂ ETL and perovskite layer. To clearly verify ELAA affecting the underlying perovskite layer, we employ epoxy resin adhering to the perovskite layer and completely peeling off the layer from the SnO₂ ETL. We systematically evaluated the properties of the SnO₂ ETL and the bottom of the perovskite layer buried at the interface with the ELAA modification. ELAA not only inhibited Sn_i defects and hydroxyl oxygen on the surface of the SnO₂ ETL, but also regulated the crystallization of perovskites to avoid the generation of defects. Besides, the incorporation of ELAA not only enhanced the optimization of the energy band structure of the SnO₂ ETL but also augmented the built-in electric field, resulting in the improvement of cell performance. As a result, ELAA-modified PSCs achieved champion PCEs of 23.43% and 20.63% on 0.09 cm² single subcells and 1.01 cm² micro-modules, respectively. Furthermore, the unencapsulated optimized device exhibited good air environment stability and illumination stability, maintaining 81% and 86% of the original PCE after aging in air for 1000 h and light for 500 h, respectively.