CsPbBr₃/p-Si membrane heterojunction photodiode: photodetection characteristics andC-Vanalysis

We report the fabrication and physical characterization of a self-driven heterojunction photodetector based on an all-inorganic CsPbBr₃thin film interfaced with a lightweight, freestanding p-type single-crystal silicon membrane (p-Si). Different from conventional rigid substrates, this membrane-based architecture leverages the superior carrier mobility and mechanical resilience of monocrystalline silicon for flexible, high-sensitivity optoelectronics. Beyond standard characterization, an Elliott-type quantum well model was employed to resolve the excitonic nature of the CsPbBr₃nanocrystals, revealing a significant exciton binding energy of 340 meV and a quasi-particle bandgap of 2.91 eV. Under zero-bias conditions, the device exhibits a robust broadband response with a peak responsivity of 0.1 A/W and a detectivity of 1.75 × 10¹¹Jones. Crucially, the strong built-in potential (V_bi= 0.91 V) facilitates efficient exciton dissociation, overcoming Coulombic attraction even at zero bias to enable high-performance self-powered operation. To elucidate the underlying transport physics, we conduct an in-depth study of the frequency-dispersive capacitance-voltage (C-V) characteristics. Our study reveals how interface states and deep-level defects dictate the steady-state photocurrent and transient kinetics (∼130 ms).C-Vanalysis further enabled the quantification of the interface trap density (D_it∼ 10¹¹eV^-1cm^-2), confirming significant interfacial defect contributions to the non-ideal device behavior. By employing a modified depletion approximation incorporating the diode ideality factor (η), we decouple parasitic trap-assisted processes from the intrinsic junction capacitance to resolve a preciseV_biof 0.91 V. This rigorous analytical approach provides critical insights into the non-ideal junction physics governing the performance of self-powered, membrane-based perovskite optoelectronics.