Piezophototronic Modulation in 2D Ruddlesden–Popper Perovskite: A Pathway to Strain–Light Synergistic Self-Powered Intelligent Sensing

Abstract

Interfacial coupling between low- dimensional halide perovskites and ferroelectric matrices provide a powerful route to amplify electromechanical and optoelectronic responses for self-powered systems. In this study, we successfully synthesized high-quality millimeter-sized single crystals of the Ruddlesden–Popper phase Butylammonium lead bromide ((C4H9NH3)2PbBr4 or BA₂PbBr4) via a solution-based method and embedded them into PVDF to fabricate high-performance piezoelectric–piezophototronic nanogenerators. Comprehensive characterization using XRD, FESEM, XPS, and UV–Vis spectroscopy confirmed the material’s phase purity, crystallinity, chemical composition, and a direct optical bandgap of ~2.95 eV. Fourier Transform Infrared (FTIR) Spectroscopy revealed a significant increase in the electroactive β-phase content (~92%) in PVDF upon incorporation of 3 wt.% BA₂PbBr4. This is attributed to the interfacial dipole locking effect, where the anisotropic 2D perovskite framework acts as a template to physically align and stabilize the polymer dipoles. Piezoresponse Force Microscopy (PFM) showed enhanced ferroelectric switching and a significantly amplified piezoelectric coefficient (d₃₃ ≈ 28.7 pm/V), compared to the bare perovskite (d₃₃ ≈ 19.8 pm/V). Density Functional Theory (DFT) analysis further confirmed strong interfacial coupling and favorable charge transfer between the PVDF and BA₂PbBr4 phases. The resulting nanogenerator device delivered an open-circuit voltage of ~103 V, a short-circuit current of ~11 μA, and a peak power of ~1.1 mW under a constant force of 12 N. It also demonstrated robust mechanical energy harvesting from various human motions, with stable output over 5,000 cycles. Real-world utility was validated by charging commercial capacitors, powering a digital smartwatch, and illuminating commercial green and red LEDs. Importantly, the device exhibited a pronounced piezophototronic effect, with enhanced current output under light illumination, confirming its photoactivity and strain-sensitive optoelectronic response. These findings underscore the multifunctional potential of PVDF/ BA₂PbBr4 composites and pave the way for their integration into next-generation wearable, self-powered energy harvesting and intelligent sensing platforms.