Output Performance Optimization of NbOCl₂‐Based 2D Piezoelectric Energy Harvester Via Synergy of Polarization Orientation and Built‐In Field for Strain Array Sensing

Abstract 2D piezoelectric devices have a bright future in wearable devices due to their conformal monitoring. However, weak performance and low information density restrict the functionality of these devices. Here, the output performance of the 2D piezoelectric energy harvesters (PEHs) is optimized through the synergistic effect of the piezoelectric polarization field and the built‐in field. 2D PEHs with a gold‐indium electrode structure have built‐in electric fields oriented in the same direction as the piezoelectric field, which increases the total polarization field to optimize the output performance and stability. The peak‐to‐peak open‐circuit voltage is up to 164.7 mV, which is 8.95 times that of the symmetric gold electrodes. The novel integrated arrays fabricated based on 2D PEHs exhibit superior overall performance compared to previously reported piezoelectric sensors, enabling the reconstruction of the surface weak strain field, benefiting from the good linear relationship between output voltage and strain. Combined with deep learning techniques, the 2D PEH integrated array recognizes eight wrist motion states of small amplitude differences with 98.44% accuracy. This work not only provides a synergistic strategy of piezoelectric orientation and built‐in fields for developing intelligent sensor arrays, but also broadens the application fields of 2D piezoelectric devices.