GeSe thin-film solar cells
Thin-film solar cells made from non-toxic and earth-abundant materials are needed to substitute the current best-developed absorbers such as cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) due to the toxicity of Cd and scarcity of In and Te. In this aspect, germanium monoselenide (GeSe) satisfies the aforementioned criteria and has recently emerged as a potential replacement. Moreover, GeSe possesses a suitable bandgap of 1.14 eV (optimal for single junction solar cells), high absorption coefficient (>105 cm−1) at a wavelength close to the absorption onset, high hole mobility (128.6 cm2 V−1 s−1), and simple binary composition with fixed orthorhombic phase at room temperature. This review introduces the properties of GeSe with special emphasis on the material, optical and electrical properties, and then summarizes the recent progress of GeSe-based solar cells. Finally, we give guidance on optimizing GeSe thin-film solar cells to their full performance potential, and provide a brief outlook for the further development of GeSe thin-film solar cells.