Improved photovoltaic performance via synergistically combining electric poling and flexoelectricity on lead-free ferroelectric (KNbO₃)_0.9(BaNi_1/2Nb_1/2O_3-δ)_0.1 films

Potassium niobate-based [(KNbO₃)_0.9(BaNi_1/2Nb_1/2O_3-δ)_0.1, abbreviated: KBNNO] ferroelectrics have recently triggered great attentions because of its unique advantages of stable structure, narrow-bandgap, good photovoltaic properties and environment-friendly composites. However, exploring new strategies to dynamically and reversibly regulate and enhance the photocurrent of KNbO₃-based thin films is still of great significance. In this work, we propose to grow flexible KBNNO thin films on an inorganic Mica substrate. The integration of in-situ electric-field poling and the strain-gradient-induced flexoelectric field enables dynamic and reversible modulation of photocurrent, thereby boosting its output performance for ferroelectric photovoltaic applications. Under a single electric field polarization, the current increases from 8.09 μA/cm² to 10.72 μA/cm², and then to 12.10 μA/cm² with the synergy of the flexoelectric effect. This work opens a promising path for the development of multifunctional flexible optoelectronic materials.