Overcoming Limitations in Water–Ethanol Sprayed Superstrate Solar Cells by Compositional Engineering of Cu₂CdSn(S,Se)₄

Abstract

The increasing demand for solar energy requires materials from earth-abundant elements to ensure cost-effective production. One such light harvester Cu2CdSn(S,Se)4 fulfills this property. We report the development of functional solar cells based on Cu2CdSn(S,Se)4, which has been previously unreported. Furthermore, we deposited the thin films of Cu2CdSn(S,Se)4 by spray pyrolysis using environmentally benign solvents, in a superstrate architecture, reducing the potential cost of upscaling, the environmental hazards, and enabling its use in semitransparent or tandem solar cells. We analyze the Cu2CdSn(S,Se)4 and its optoelectronic characteristics with different sulfur and selenium ratios in the composition. We noted that Se is homogeneously distributed in the absorber and electron transport layer, forming a Cd(S,Se) phase that impacts the optoelectronic properties. The introduction of Se, up to 30%, is found to have a positive impact on the solar cell performance, largely improving the fill factor and absorption in the infrared region, while the voltage deficit is reduced. The device with a Cu2CdSn(S2.8Se1.2) composition had a 3.5% solar-to-electric conversion efficiency, which is on par with the reported values for chalcogenides and the first report using Cu2CdSn(S,Se)4. We identified the critical factors that limit the efficiency, revealing pathways to further reduce the losses and improve the performance. This work provides the first proof of concept of a novel material, paving the way for developing cost-efficient solar cells based on earth-abundant materials.

A Comprehensive Review on the Recent Strategy of Cation Substitution in CZTS(Se) Thin Films to Achieve Highly Efficient Kesterite Solar Cells

“…Recently, in 2023, Zarceño et al reported the deposition of thin films of Cu 2 CdSn(S,Se) 4 by spray pyrolysis using environmentally benign solvents to fabricate thin-film solar cells in a superstrate architecture to reduce the potential cost of upscaling, the environmental hazards, and enable its use in semitransparent or tandem solar cells. [72] To mitigate the problematic interface with both the Mo/Mo(S,Se) back contact and the CdS front contact, they have used kesterite in a superstrate architecture which is rapidly evolving as an alternative to improve the interfaces while reducing the processing cost of solar cells. Deep work function (5 eV) of graphite makes it a suitable cheaper choice for hole-transporting layer.…”

“…Recently, in 2023, Zarceño et al reported the deposition of thin films of Cu 2 CdSn(S,Se) 4 by spray pyrolysis using environmentally benign solvents to fabricate thin‐film solar cells in a superstrate architecture to reduce the potential cost of upscaling, the environmental hazards, and enable its use in semitransparent or tandem solar cells. [ 72 ] To mitigate the problematic interface with both the Mo/Mo(S,Se) back contact and…”