Signal Formation in Photon Counting Perovskite Detectors

This dissertation investigates organic–inorganic halide perovskites as radiation detectors across indirect scintillator-coupled and direct ionizing detection architectures. Although these systems share common material platforms, their governing physical constraints and optimization strategies differ substantially. Polycrystalline photodetectors operating in indirect configurations are demonstrated as low-energy photon-counting readouts in two scintillator-coupled architectures using MAPbI$_3$-based devices. Time-domain signal analysis provides insight into comparative detector stack performance and system-level limitations. Wider band gap FAPbBr$_{3-X}$Cl$_X$ films are further optically and structurally characterized to establish compatibility with scintillators emitting at shorter wavelengths. In contrast, single-crystal FAPbBr$_3$ devices operating in direct detection mode are examined through ionization statistics, trap-mediated carrier dynamics, electrostatic boundary conditions, and readout constraints. Time-domain digital signal processing methods are developed to resolve direct and delayed charge collection within individual waveforms, enabling separation of shallow and deep trap contributions during real-time gamma detection. Surface passivation is shown to improve charge collection efficiency and spectral clarity while increasing delayed carrier collection within finite integration windows. Charge sharing in pixelated single-crystal detectors is further investigated through electrostatic modeling, sub-pixel optical excitation, and ionizing radiation measurements. Induced charge sharing governed by weighting potential overlap is experimentally decoupled from transport-mediated lateral diffusion. Guard-ring architecture and bias conditions are identified as primary controls for suppressing multi-pixel coupling while preserving spectral performance. Across both detector classes, recurring trade-offs emerge between passivation and temporal response, thickness and lateral charge spread, guard width and active area, and shaping time and event retention. These findings demonstrate that high-performance perovskite radiation detection requires coordinated optimization of material quality, electrostatic design, device geometry, and signal processing parameters. When these factors are treated explicitly, detector behavior becomes predictable and tunable rather than empirical, advancing perovskite-based systems toward scalable photon-counting and spectral imaging applications.