Anti-perovskite carbides Ca6CSe4 and Sr6CSe4 for photovoltaics with similar optoelectronic properties to MAPbI3. Issue 40 (27th September 2022) - Guo, Wen-hui
Abstract : Anti-perovskite carbides Ca6CSe4 and Sr6CSe4 with PCE of 31% comparable with MAPbI3 . Abstract : Anti-perovskites with better stability than halide perovskites demonstrate great potential as stable photovoltaic materials. In recent years, a few anti-nitride and -oxide perovskites have been designed as solar cell absorbers, however, anti-carbide perovskites have yet to be investigated for photovoltaic applications. Herein, through first-principles calculations, environmentally friendly anti-perovskite carbides M6 CCh4 (M = Ca, Sr, Ba; Ch = S, Se, Te) with good stability are anticipated, which arise from the stable Cs4 PbX6 -perovskite structure. Unlike the isolated [PbX6 ] octahedra in Cs4 PbX6, the covalent bonding feature of C–Ch bonds makes the [M6 C] octahedra connected in M6 CCh4 advantageous for photo-induced carrier transport. They also show low carrier effective mass (0.2 m 0 ), small exciton binding energy (30–80 meV), and strong dielectric screening, causing high carrier mobility up to 300 cm 2 V −1 s −1 . Among the M6 CCh4 anti-perovskites, Ca6 CSe4 and Sr6 CSe4 with similar optoelectronic properties to MAPbI3 (MA = CH3 NH3 ) are screened as the best single-junction solar-cell absorbers. Their suitable direct bandgap (1.50 eV) and dipole-allowed optical transitions between band edges result in strong visible-light absorption (2 × 10 5 cm −1 ). The large simulated power conversion efficiency of 31% is implemented in Ca6 CSe4 and Sr6 CSe4 . The prediction of anti-carbide perovskites M6 CCh4 provides a novel perspective on high-performance optoelectronic materials.