Chiral Two-Dimensional Perovskite Single Crystals Enable Flexible Piezoelectric Nanogenerators for High-Sensitivity Ultrasound Detection

Hybrid perovskites are emerging as promising piezoelectric materials, yet the use of high-quality single crystals in flexible ultrasound sensing remains largely unexplored. Here, we report intrinsically noncentrosymmetric chiral two-dimensional perovskite single crystals, (S/R-NEA)2PbBr4, that exhibit strong piezoelectricity arising from chirality-induced symmetry breaking and enhanced lattice polarizability. By integrating these crystals into a polymer matrix, we realize flexible piezoelectric nanogenerators delivering high output (∼8 V) under ultrasonic excitation. The devices enable reliable detection and clear resolution of 50 kHz ultrasound signals, along with excellent mechanical durability and environmental stability. This work establishes a single-crystal strategy for flexible piezoelectric devices and highlights chiral 2D perovskites as a compelling platform for high-sensitivity ultrasound detection and energy harvesting.