Energie landschap van dunne film beeldsensors

Thin-film infrared photodiodes offer a low-cost, large-area, and CMOS-compatible alternative to traditional III-V semiconductor detectors, whose reliance on costly epitaxy and flip-chip bonding results in resolution limitations and expensive process flows. Despite progress in thin film organic semiconductors and colloidal quantum dots (CQDs), achieving low-dark-current operation with controlled energy alignment remains a major challenge. Process variability, surface chemistry sensitivity, and incomplete understanding of how thin-film energetics evolve within a full device stack limit reproducibility and performance. This thesis addresses the broader question of how the energy landscape and underlying physical processes in thin-film near and short-wave infrared (NIR and SWIR) photodiodes can be systematically mapped and understood to uncover the origin of dark noise and develop strategies for its reduction. To achieve this, energetic analysis is paired with advanced electrical, optical, and transient characterization techniques, creating a comprehensive framework that connects material and interface properties to operational device performance. The first part focuses on organic bulk heterojunction NIR photodiodes, where interface engineering using C60:LiF layers was applied to suppress trap-assisted leakage without compromising external quantum efficiency or speed. A combination of ultraviolet photoemission spectroscopy, temperature-dependent current-voltage measurements, Poole-Frenkel analysis, and transient techniques quantified the role of the engineered interface in modifying energy levels, reducing trap density, and improving carrier lifetime. The second part examines PbS and InAs CQD thin films, emphasizing the effect of solid-state ligand exchange chemistry on energy band shifts. Here, a comprehensive understanding of how CQD density and dispersion influence the measured energy band structure is achieved by correlating morphological insights from transmission electron microscopy (TEM) with photoemission spectroscopy across different ligand chemistries. The final part presents the development of a CMOS-compatible heavy-metal-free InAs CQD photodiode featuring a newly introduced and uniquely optimized combination of hole and electron transport layers, tailored to achieve more favorable energetic alignment. This design delivered one of the highest reported performances at 1200 nm for heavy-metal-free CQDs. A comprehensive analysis of dark carrier dynamics was carried out, combining temperature-dependent capacitance-frequency measurements, current-voltage characterization, and space-charge-limited conduction analysis. These studies identified surface passivation and ligand chemistry as fundamental bottlenecks, directly influencing dark noise levels and limiting further performance improvements. Both the OPD and the optimized InAs CQD stacks were monolithically integrated onto CMOS readout integrated circuits (ROICs) for infrared imaging. Imaging under infrared illumination at 940 nm and 1200 nm demonstrated material-specific infrared contrast, highlighting the potential of these thin-film photodiodes for CMOS-compatible infrared imaging applications.