Overcoming Field-Assisted Leakage and Mobility Deficits in InAs Colloidal Quantum Dot SWIR Photodetectors

InAs colloidal quantum dots (CQDs) synthesized using non-pyrophoric precursors are attractive for short-wave infrared (SWIR) photodetection, yet their device performance remains limited by low external quantum efficiency (EQE) and high dark current. Here, we attribute these limitations to two material-level impediments: poor carrier mobility and broadly distributed sub-bandgap states. To address the former, we adapt a butylamine-assisted InBr3 ligand-exchange process, which increases carrier mobility by ∼80-fold and enhances EQE from 11% to 25% at -1 V. Temperature-dependent electrical and defect analyses reveal that field-assisted leakage current arises from sub-bandgap states associated with agglomerated, irregularly shaped particles within the CQD ensemble. Removing these particles via size-selective precipitation reduces trap density, increases trap activation energy, and suppresses dark current by an order of magnitude. Together, these complementary strategies yield InAs CQD photodetectors with a shot-noise-estimated detectivity of 9.8 × 1010 jones at 1320 nm and a rise time of 32 ns at -0.5 V.