Design and Optimization of Vertical FTO/BaHfS₃/Au Devices: Thickness, Interface and Contact Effects

This study presents a numerical investigation of vertical devices based on the lead-free chalcogenide perovskite , focusing on the effects of absorber thickness, metal contact work function, and interface quality on device performance. Using SCAPS-1D simulations, we systematically analyzed devices. The results show that the absorber thickness critically influences the photocurrent density, with an optimal range between 600 and 1000 nm, where increased light absorption is balanced against rising bulk recombination. Impedance spectroscopy reveals that thicker absorbers enhance charge transfer resistance, thereby improving carrier collection under the simulated conditions. Specific detectivity ( ) rises monotonically with absorber thickness, from 2.04×10¹³ Jones to 5.94×10¹³ Jones, and similarly improves with higher work‑function back contacts; increased contact work function reduces the effective Schottky barrier at the semiconductor–metal interface, suppresses thermionic dark current and facilitates hole extraction, yielding concurrent improvements in responsivity and . Low interface defect densities are shown to be essential for minimizing dark current and achieving high external quantum efficiency. These findings provide a comprehensive design roadmap for optimizing -based vertical photodiodes and photodetectors, positioning them as promising candidates for stable, high-sensitivity, and environmentally benign optoelectronic applications.