Non-polar surface passivation of PbS Quantum Dots using metal thiolates enables photodiodes rivaling InGaAs performance

Colloidal quantum dots (CQDs) short-wave infrared (SWIR) detectors (1-2 µm) are of great interest for a plethora of applications including autonomous driving, machine vision, night and adverse weather imaging, in view of their low-cost and compatibility to read-out electronics. However, to date, CQDs photodetectors still suffer from high dark current and thereby noise such that their performance remains inferior to epitaxially grown III-V semiconductors. This performance gap originates from the limited passivation of non-polar surfaces existent in large PbS CQDs needed to access the SWIR spectral range. Here we report on a lead-thiolate based chemistry that serves to passivate both polar and non-polar surfaces of PbS CQDs yielding inks with unprecedented optoelectronic quality evidenced by open circuit voltage deficit and dark current activation energies matching those of single crystalline semiconductors. As a result, we demonstrate infrared photodetectors with remarkable thermal resilience, very low dark current density ( ~ 34 nA cm −2 at −1 V) and a specific detectivity D* of ~8×10 12 Jones. The measured D* value is on par with that of commercially available InGaAs photodiodes (PDs).