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.