Parallel Planar Heterojunction Strategy Enables Sb2S3 Solar Cells with Efficiency Exceeding 8 %

Abstract Solution‐processed solar cells based on inorganic heterojunctions provide a potential approach to the efficient, stable and low‐cost solar cells required for the terrestrial generation of photovoltaic energy. Antimony trisulfide (Sb 2 S 3 ) is a promising photovoltaic absorber. Here, an easily solution‐processed parallel planar heterojunction (PPHJ) strategy and related principle are developed to prepare efficient multiple planar heterojunction (PHJ) solar cells, and the PPHJ strategy boosts the efficiency of solution‐processed Sb 2 S 3 solar cells up to 8.32 % that is the highest amongst Sb 2 S 3 devices. The Sb 2 S 3 ‐based PPHJ device consists of two kinds of conventional planar heterojunction (PHJ) subcells in a parallel connection: Sb 2 S 3 ‐based PHJ subcells dominating the absorption and charge generation and CH 3 NH 3 PbI 3 ‐based PHJ subcells governing the electron transport towards collection electrode, but it belongs to an Sb 2 S 3 device in nature. The resulting PPHJ device combines together the distinctive structural features of Sb 2 S 3 absorbing layer as a main absorber and the duplexity of well‐crystallized/oriented CH 3 NH 3 PbI 3 layer in charge transportation as an additional absorber, while the presence of perovskite does not affect device stability. The PPHJ strategy maintains the facile preparation by the conventional sequential depositions of multiple layers, but eliminates the normal complexity in both tandem and parallel tandem PHJ systems.