Revealing Additional Size-Dependent Defect Suppression Channels Governing Detectivity in InAs Colloidal Quantum Dot...

Indium arsenide (InAs) colloidal quantum dot (CQD) photodiodes combine tunable bandgaps with solution processing, offering a versatile platform for infrared detection. Using high-dynamic-range external quantum efficiency (HDR-EQE) measurements, we probe defect signatures and quantify their impact on performance. Analysis of Urbach tails and Gaussian sub-bandgap states shows that trap densities decrease with increasing nanocrystal size, exceeding predictions from simple surface-to-volume scaling and underscoring the influence of surface chemistry on bandedge disorder. These defect states affect the dark saturation current (J₀), enabling us to estimate their contribution to detectivity and noise. The results connect nanocrystal size, defect population, and device performance, distinguishing intrinsic trap-mediated effects from extrinsic loss channels. We find that while intrinsic defects play a role, today's InAs CQD photodiodes are primarily limited by contact and interface properties, highlighting these as key targets for further improvement.