Piezophototronic modulation in a 2D Ruddlesden–Popper perovskite: a pathway to strain–light synergistic self-powered intelligent sensing

Interfacial coupling between low-dimensional halide perovskites and ferroelectric matrices provides a powerful route to amplify electromechanical and optoelectronic responses for self-powered systems. We synthesized millimeter-sized high-quality 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. 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. The FTIR study revealed a significant increase in the electroactive β-phase content (∼92%) in PVDF upon incorporation of 3 wt% BA₂PbBr₄, attributed to the interfacial dipole locking effect where the anisotropic 2D perovskite framework aligns and stabilizes polymer dipoles. The PFM study showed enhanced ferroelectric switching and an amplified piezoelectric coefficient (d₃₃ ≈ 28.7 pm V^-1), compared to a bare perovskite (d₃₃ ≈ 19.8 pm V^-1). DFT analysis confirmed strong interfacial coupling and favorable charge transfer between the building blocks. The nanogenerator 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, with stable output over 5000 cycles. It harvested mechanical energy from human motions and powered capacitors, a smartwatch, and LEDs. Importantly, the device exhibited a pronounced piezophototronic effect, with enhanced current under illumination, confirming photoactivity and strain-sensitive optoelectronic response. Notably, simultaneous application of mechanical strain and visible light illumination resulted in a synergistic 5.8-fold enhancement in photocurrent, enabling the successful demonstration of a mechano-optical logic OR gate. These results highlight the multifunctional potential of PVDF/BA₂PbBr₄ composites for next-generation wearable, self-powered energy harvesting and intelligent sensing platforms.