Simultaneous improvement of polarization and bandgap by finite solid solution engineering.

A narrow-bandgap-induced potential field always results in decreased photovoltaic performance. Here, a finite solid solution was designed to explore the simultaneous improvement of the polarization property and bandgap obtained from the critical effect in which BiMnO 3 (BM) enters the Na 0.5 Bi 0.5 TiO 3 (NBT) crystal lattice, resulting in a strong lattice expansion; by contrast, the incorporation of Mn without a d-orbital weakened the orbital hybridization accompanied by Jahn-Teller (J-T) distortion to reduce the optical bandgap. A narrow bandgap of 2.90 eV and polarization of 65.9 μC cm -2 were achieved by finite solid solution engineering. The open-circuit voltage and the short-circuit current with a BM doping component of 0.04 reached as high as 1.1 V and 0.0132 mA cm -2 , respectively. This work provides an optimized strategy for the mutual benefit of the polarization and bandgap by finite solid solution engineering.