Control over Charge Carrier Mobility in the Hole Transport Layer Enables Fast Colloidal Quantum Dot Infrared Photodetectors

Solution-processedcolloidal quantum dots (CQDs) are promisingmaterials for photodetectors operating in the short-wavelength infraredregion (SWIR). Devices typically rely on CQD-based hole transportlayers (HTL), such as CQDs treated using 1,2-ethanedithiol. Herein,we find that these HTL materials exhibit low carrier mobility, limitingthe photodiode response speed. We develop instead inverted (p-i-n)SWIR photodetectors operating at 1370 nm, employing NiOx as the HTL,ultimately enabling 4x shorter fall times in photodiodes (similar to 800ns for EDT and similar to 200 ns for NiOx). Optoelectronic simulationsreveal that the high carrier mobility of NiOx enhances the electricfield in the active layer, decreasing the overall transport time andincreasing photodetector response time.