High-performance PbS colloidal quantum dot photodiode for short-wave infrared imaging based on energy band alignment engineering

Lead sulfide (PbS) colloidal quantum dots (CQDs) are widely used for infrared detection and imaging. Currently, the most popular device structures for PbS CQDs photodetectors (PDs) are p-i-n type. Among them, the PbS CQDs films treated with 1,2-ethanedithiol (EDT) are extensively utilized as hole transport layers. However, the energy band alignment based on the PbS-EDT layer has a great impact on the device performance and has not been thoroughly investigated. To systematically explore the effect of the bandgap of PbS-EDT layer on device performance, this work is firstly based on the PbS-EDT layer simulated through SCAPS-1D software. When the PbSEDT layer bandgap is 1.4 eV, the device can build a suitable gradient energy band structure and the dark current density (Jdark) reaches the lowest. Based on the simulation results, the corresponding PbS CQDs PDs were fabricated, which showed excellent performance with the Jdark of 265 nA/cm2 at a bias voltage of-0.5V, the responsivity and specific detectivity reached 0.65 A/W and 5.73 x 1012Jones, respectively. A single-element scanning infrared imaging system demonstrates the excellent imaging capability of the device. The energy band alignment strategy based on the PbS-EDT layer is expected to promote infrared optoelectronic applications in this field.