Screening and optimization of processing temperature for Sb2Se3 thin film growth protocol: Interrelation between grain structure, interface intermixing and solar cell performance

Deliverability of controllable deposition processes represents the current state-of-the-art strategy for the development of emerging 1D crystal-structure photovoltaic (PV) materials. For Sb2Se3, a compound with tremendous potential for next-generation cost-efficient thin-film PV, the current reported findings proposed that columnar grain growth protocol is required to promote efficient carrier transport and to achieve highly efficient solar cells. It is still a matter of debate, however, whether the growth of the thin-film absorber should follow the weak contacted nanorod grain structure or the columnar-sintered large grain protocol, in relation with the processing temperature, the under-layer junction partner, and interface intermixing. In this work, close-spaced sublimation processing temperature in conjunction with CdS and TiO2 junction partner layers is systematically investigated towards optimization of Sb2Se3 thin film growth conditions. The desideratum of columnar-sintered large grains protocol is validated and insights into the mechanism of absorber-buffer interface intermixing are provided. Following a systematical technological approach, a solar cell efficiency of 5.3% is demonstrated. Combining classical and advanced measurement techniques, insights into physicochemical processes and device functionality in connection with grain structure, defect density, carrier concentration, and recombination mechanism in Sb2Se3 absorber are provided.