Effective bandgap narrowing and enhanced optoelectronic performance of CsPtBr double perovskites by pressure engineering.

Tuning the structure-property relations of perovskites by pressure engineering holds great promise for discovering materials with favorable properties. The newly synthesized CsPtBr double perovskite exhibits excellent water resistance and chemical stability. Yet its photoelectric conversion efficiency is limited by its intrinsic wide-bandgap nature. In this work, based on density functional theory calculations, we demonstrate the bandgap narrowing of CsPtBr via pressure engineering and maintain its structural stability. Strikingly, upon applying pressure up to 12 GPa, the bandgap value decreases to 1.34 eV, which exactly reaches the optimal bandgap required by the Shockley-Queisser efficiency limit. Moreover, optical calculation analysis shows that the optical absorption of CsPtBr exhibits a significant improvement within the visible range. Therefore, the potential of CsPtBr as a photovoltaic material by pressure engineering is improved. This work is useful for designing and synthesizing new perovskite materials with enhanced performance.