Grain Engineering of Sb2 S3 Thin Films to Enable Efficient Planar Solar Cells with High Open-Circuit Voltage.

ABSTRACT

Sb2 S3 is a promising environmentally friendly semiconductor for high performance solar cells. But, like many other polycrystalline materials, Sb2 S3 is limited by nonradiative recombination and carrier scattering by grain boundaries (GBs). This work shows how the GB density in Sb2 S3 films can be significantly reduced from 1068 ± 40 to 327 ± 23 nm µm-2 by incorporating an appropriate amount of Ce3+ into the precursor solution for Sb2 S3 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 Ce2 S3 layer at the CdS/Sb2 S3 interface, which can reduce the interfacial energy and increase the adhesion work between Sb2 S3 and the substrate to encourage heterogeneous nucleation of Sb2 S3 , as well as promote lateral grain growth. Through reductions in nonradiative recombination at GBs and/or the CdS/Sb2 S3 heterointerface, as well as improved charge-carrier transport properties at the heterojunction, this work achieves high performance Sb2 S3 solar cells with a power conversion efficiency reaching 7.66%. An impressive open-circuit voltage (VOC ) of 796 mV is achieved, which is the highest reported thus far for Sb2 S3 solar cells. This work provides a strategy to simultaneously regulate the nucleation and growth of Sb2 S3 absorber films for enhanced device performance.