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

Binary compound antimony sulfide (Sb₂S₃) 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 Sb₂S₃ is known to transfer photogenerated carriers rapidly along the [hk1] orientation. However, producing Sb₂S₃ devices with precise control of [hk1] orientation is challenging and unfavorable crystal orientations of Sb₂S₃ result in severe interface and bulk recombination losses. Herein, in situ vertical growth of Sb₂S₃ on top of ultrathin TiO₂/CdS as the electron transport layer (ETL) by a solution method is demonstrated. The planar heterojunction solar cell using [hk1]-oriented Sb₂S₃ 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 Sb₂S₃ thin film solar cells by tailoring the crystal orientation.