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

Theincreasing demand for solar energy requires materials fromearth-abundant elements to ensure cost-effective production. One suchlight harvester Cu2CdSn-(S,Se)(4) fulfills thisproperty. We report the development of functional solar cells basedon Cu2CdSn-(S,Se)(4), which has been previouslyunreported. Furthermore, we deposited the thin films of Cu2CdSn-(S,Se)(4) by spray pyrolysis using environmentally benignsolvents, in a superstrate architecture, reducing the potential costof upscaling, the environmental hazards, and enabling its use in semitransparentor tandem solar cells. We analyze the Cu2CdSn-(S,Se)(4) and its optoelectronic characteristics with different sulfurand selenium ratios in the composition. We noted that Se is homogeneouslydistributed in the absorber and electron transport layer, forminga Cd-(S,Se) phase that impacts the optoelectronic properties. The introductionof Se, up to 30%, is found to have a positive impact on the solarcell performance, largely improving the fill factor and absorptionin the infrared region, while the voltage deficit is reduced. Thedevice with a Cu2CdSn-(S2.8Se1.2)composition had a 3.5% solar-to-electric conversion efficiency, whichis on par with the reported values for chalcogenides and the firstreport using Cu2CdSn-(S,Se)(4). We identified thecritical factors that limit the efficiency, revealing pathways tofurther reduce the losses and improve the performance. This work providesthe first proof of concept of a novel material, paving the way fordeveloping cost-efficient solar cells based on earth-abundant materials.

Automated summary

The increasing demand for solar energy necessitates the use of earth-abundant materials for cost-effective production. Cu2CdSn-(S,Se)(4), a light harvester with this property, is shown to have potential for functional solar cells. Thin films of Cu2CdSn-(S,Se)(4) were deposited using environmentally friendly solvents, reducing costs and enabling use in semitransparent or tandem solar cells. The introduction of selenium in the composition improves the solar cell performance, and a device with Cu2CdSn-(S2.8Se1.2) composition achieved a 3.5% conversion efficiency.