Poly(vinylidene fluoride)-Stabilized Black γ-Phase CsPbI Perovskite for High-Performance Piezoelectric Nanogenerators.

Halide perovskite materials have been recently recognized as promising materials for piezoelectric nanogenerators (PENGs) due to their potentially strong ferroelectricity and piezoelectricity. Here, we report a new method using a poly(vinylidene fluoride) (PVDF) polymer to achieve excellent long-term stable black γ-phase CsPbI and explore the piezoelectric performance on a CsPbI@PVDF composite film. The PVDF-stabilized black-phase CsPbI perovskite composite film can be stable under ambient conditions for more than 60 days and over 24 h while heated at 80 °C. Piezoresponse force spectroscopy measurements revealed that the black CsPbI/PVDF composite contains well-developed ferroelectric properties with a high piezoelectric charge coefficient ( ) of 28.4 pm/V. The black phase of the CsPbI-based PVDF composite exhibited 2 times higher performance than the yellow phase of the CsPbI-based composite. A layer-by-layer stacking method was adopted to tune the thickness of the composite film. A five-layer black-phase CsPbI@PVDF composite PENG exhibited a voltage output of 26 V and a current density of 1.1 μA/cm. The output power can reach a peak value of 25 μW. Moreover, the PENG can be utilized to charge capacitors through a bridge rectifier and display good durability without degradation for over 14 000 cyclic tests. These results reveal the feasibility of the all-inorganic perovskite for the design and development of high-performance piezoelectric nanogenerators.