Ultralow Dark Current Density in PbS Colloidal Quantum Dot Short-Wave Infrared Photodetectors with Homogeneous Energy...

Colloidal quantum dot (CQD) thin films hold promise for low-cost and high-resolution short-wave infrared imaging, yet their performance is hindered by an inhomogeneous energy landscape arising from the CQD synthetic polydispersity and ligand exchange process. Herein, by adopting a mild solvent in the solid-state ligand exchange process, this process transitions from kinetically favorable to thermodynamically stable, thereby obtaining the PbS CQD film with a homogeneous energy landscape. The optimal CQD film exhibits a sharp bandtail and largely reduced density of trap states, effectively suppressing thermal carrier generation and a trap-associated generation-recombination process. Consequently, the photodetector achieves an ultralow reverse-bias dark current density (J_dark) of 5.8 × 10^-9 A cm^-2 at -0.3 V. This is among the lowest reported J_dark to date. Furthermore, efficient carrier extraction to the electron acceptor is achieved under zero bias conditions, and the photocurrent exhibits weak dependence on reverse bias, both helpful for attaining linear output in the source-follower scheme.