Earth-Abundant Orthorhombic BaCu₂Sn(Se_xS_1–x)₄ (x ≈ 0.83) Thin Film for Solar Energy Conversion

Exploiting renewable solar energy in terms of solar-driven water splitting and photovoltaic devices provides clean and efficient paths to overcome diminishing fossil fuel resources and the greenhouse effect. Here, a state-of-the-art earth-abundant BaCu 2 Sn(Se 0.83 S 0.17 ) 4 (BCTSSe) thin film has been presented as a promising top-cell absorber in tandem photoelectrochemical water splitting and photovoltaic conversion devices. Our BCTSSe thin film exhibits a direct bandgap of 1.85 eV with strong optical absorption coefficients (α > 10 4 cm –1 ). Without extensive interface and electrode optimization, our best BCTS photoelectrochemical cell showed a photocurrent of 5 mA cm –2 at 0 V vs reversible hydrogen electrode. Moreover, our best-performing BCTSSe prototype photovoltaic cell with a configuration of fluorine-doped SnO 2 (FTO, back contact)/BCTSSe/CdS/ZnO/aluminum doped ZnO (AZO, front contact) has achieved an efficiency of 1.57%.