Grain Engineering of Sb2S3 Thin Films to Enable Efficient Planar Solar Cells with High Open‐Circuit Voltage

Abstract Sb 2 S 3 is a promising environmentally friendly semiconductor for high performance solar cells. But, like many other polycrystalline materials, Sb 2 S 3 is limited by nonradiative recombination and carrier scattering by grain boundaries (GBs). This work shows how the GB density in Sb 2 S 3 films can be significantly reduced from 1068 ± 40 to 327 ± 23 nm µm −2 by incorporating an appropriate amount of Ce 3+ into the precursor solution for Sb 2 S 3 deposition. Through extensive characterization of structural, morphological, and optoelectronic properties, complemented with computations, it is revealed that a critical factor is the formation of an ultrathin Ce 2 S 3 layer at the CdS/Sb 2 S 3 interface, which can reduce the interfacial energy and increase the adhesion work between Sb 2 S 3 and the substrate to encourage heterogeneous nucleation of Sb 2 S 3 , as well as promote lateral grain growth. Through reductions in nonradiative recombination at GBs and/or the CdS/Sb 2 S 3 heterointerface, as well as improved charge‐carrier transport properties at the heterojunction, this work achieves high performance Sb 2 S 3 solar cells with a power conversion efficiency reaching 7.66%. An impressive open‐circuit voltage ( V OC ) of 796 mV is achieved, which is the highest reported thus far for Sb 2 S 3 solar cells. This work provides a strategy to simultaneously regulate the nucleation and growth of Sb 2 S 3 absorber films for enhanced device performance.