New Layered II–III–VI Semiconductors: Promising Materials for High Performance Solar Cells
Di Zhang, Bing Wang, Yu Gan, Jian Zhou, Zhimei Sun
Abstract
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 (10 4 –10 5 cm –1 ), small carrier effective masses (≤0.26 m 0 ), favorable carrier mobilities (145.5–569.7 cm 2 /(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.