In Situ Growth of [hk1]‐Oriented Sb2S3 for Solution‐Processed Planar Heterojunction Solar Cell with 6.4% Efficiency

Abstract Binary compound antimony sulfide (Sb 2 S 3 ) with its nontoxic and earth‐abundant constituents, is a promising light‐harvesting material for stable and high efficiency thin film photovoltaics. The intrinsic quasi‐1D (Q1D) crystal structure of Sb 2 S 3 is known to transfer photogenerated carriers rapidly along the [hk1] orientation. However, producing Sb 2 S 3 devices with precise control of [hk1] orientation is challenging and unfavorable crystal orientations of Sb 2 S 3 result in severe interface and bulk recombination losses. Herein, in situ vertical growth of Sb 2 S 3 on top of ultrathin TiO 2 /CdS as the electron transport layer (ETL) by a solution method is demonstrated. The planar heterojunction solar cell using [hk1]‐oriented Sb 2 S 3 achieves a power conversion efficiency of 6.4%, performing at almost 20% higher than devices based on a [hk0]‐oriented absorber. This work opens up new prospects for pursuing high‐performance Sb 2 S 3 thin film solar cells by tailoring the crystal orientation.