Parallel Planar Heterojunction Strategy Enables Sb₂ S₃ Solar Cells with Efficiency Exceeding 8 

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 (Sb₂ S₃ ) 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 Sb₂ S₃ solar cells up to 8.32 % that is the highest amongst Sb₂ S₃ devices. The Sb₂ S₃ -based PPHJ device consists of two kinds of conventional planar heterojunction (PHJ) subcells in a parallel connection: Sb₂ S₃ -based PHJ subcells dominating the absorption and charge generation and CH₃ NH₃ PbI₃ -based PHJ subcells governing the electron transport towards collection electrode, but it belongs to an Sb₂ S₃ device in nature. The resulting PPHJ device combines together the distinctive structural features of Sb₂ S₃ absorbing layer as a main absorber and the duplexity of well-crystallized/oriented CH₃ NH₃ PbI₃ 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.