Earth-Abundant Orthorhombic BaCu₂Sn(Se_<i>x</i>S_1–<i>x</i>)₄ (<i>x</i> ≈ 0.83) Thin Film for Solar Energy Conversion

Abstract

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 BaCu2Sn(Se0.83S0.17)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 > 104 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 SnO2 (FTO, back contact)/BCTSSe/CdS/ZnO/aluminum doped ZnO (AZO, front contact) has achieved an efficiency of 1.57%.