Solution-processed quantum dot short-wavelength infrared photodetectors via integrating 2D MXenes into electron transport layer

Abstract

Solution-processed quantum dots (QDs) have attracted intensive attention in short-wavelength infrared (SWIR) photodetectors due to their excellent optical properties and tunable size-dependent bandgap. However, the intrinsic defects of the widely used ZnO electron-transport layer (ETL) and the inappropriate band alignment at the interface between the ETL and photoactive QDs inevitably impact the optoelectronic performance of the photodetector. Herein, a high-performance self-powered SWIR photodetector is developed by using 2D Ti3C2 MXenes to passivate the defects of ZnO ETL and to tailor the band alignment at the interface of the ETL/photoactive layer through interface engineering. As a result, the SWIR photodetectors demonstrate the ultra-high light-to-dark current (Ilight/Idark) ratio of ∼ 105 and the low dark current density of 8.33 × 10-4 mA/cm2, and the high specific detectivity (D*) of 1.99 × 1011 Jones at 0 V. By the systematic characterizations, it is proofed that 2D MXene can efficiently passivate defects in ZnO and optimize the alignment of energy levels between the ETL and photoactive layer, which will suppress the recombination of electrons and holes and eventually promote photogenerated carrier transfer at the interface and thus improve device performance. This work revealed that the high-performance solution-processed QD based SWIR photodetector enabled by interface engineering will promote the development of optoelectronic devices in the future.