New Layered II−III−VI Semiconductors: Promising Materials for High Performance Solar Cells

Searching for materials with outstanding electronic and optical properties is of great importance for optoelectronic applications. Here, by means of high-throughput ab initio calculations, we have identified a new class of 18 layered semiconducting II−III−VI (II = Be, Mg, Ca, Sr, Ba; III = B, Al, Ga, In; VI = S, Se, Te) compounds exhibiting remarkable photovoltaic performance for the conversion of solar energy. These novel ternary compounds are predicted to show robust thermodynamic, mechanical, dynamical, and thermal stability. Importantly, at a film thickness of 2 μm, the top six direct-bandgap semiconductors show high photovoltaic conversion efficiencies of 28.7−31.6%, comparable to the currently most efficient single-junction solar cell GaAs (29.1%). Such remarkable photovoltaic performance is attributed to the optimal electronic bandgaps (1.00−1.35 eV), strong visible-light absorption coefficients (10⁴−10⁵ cm⁻¹), small carrier effective masses (≤0.26m₀), favorable carrier mobilities (145.5−569.7 cm²/(V s)), and moderate exciton binding energies (≤113.2 meV). Moreover, the electronic band structures of the indirect-bandgap semiconductors can be tuned by strain engineering, resulting in an indirect-to-direct-bandgap transition. This work not only predicts several new semiconductors with high photovoltaic performance but also offers a design strategy to explore various functional materials (Figure Presented).