Highly efficient, eco-friendly, flexible piezoelectric nanogenerators based on MA2CuCl4 NPs embedded into a zein matrix

Eco-friendly, piezoelectric MA2CuCl4-zein nanocomposites (NCs) are fabricated using the sol-gel method in which lead-free halide perovskite MA2CuCl4 nanoparticles (NPs) are successfully embedded in a natural polymer zein matrix without chemical decomposition. The MA2CuCl4-zein NCs are utilized as the piezoelectric layer for piezoelectric nanogenerators (PENGs), and PENGs based on the MA2CuCl4-zein NCs are compared with those based on MA2CuCl4 NPs and on zein. The average output voltage of the PENGs based on the MA2CuCl4-zein NCs under vertical pressure is 48.84 V, which is significantly larger than that of the PENGs with MA2CuCl4 NPs alone and with zein alone by factors of 13.49 and 4.62, respectively. The significantly higher output voltage of the PENGs based on the MA2CuCl4-zein NC thin films is attributed to enhanced piezoelectricity and the surface planarization caused by the zein matrix. The output voltages of the rigid PENG and the flexible TENG based on the MA2CuCl4-zein NC thin films remain stable without degradation after 500 taps and after 500 bends, respectively. The flexible PENGs based on MA2CuCl4-zein NC thin films can be operated using various human motions, such as bending with fingers, the palms of hands, and or the arms, and stepping on the PENGs. The utilization of MA2CuCl4-zein NCs provides insight into developing eco-friendly PENGs that utilize lead-free halide perovskites and natural polymers.