Recent progress of infrared photodetectors based on lead chalcogenide colloidal quantum dots

Abstract

Commercial photodetectors based on silicon are extensively applied in numerous fields. Except for their high performance, their maximum absorption wavelength is not over than 1100 nm and incident light with longer wavelengths cannot be detected; in addition, their cost is high and their manufacturing process is complex. Therefore, it is meaningful and significant to extend absorption wavelength, to decrease cost, and to simplify the manufacturing process while maintaining high performance for photodetectors. Due to the properties of size-dependent bandgap tunability, low cost, facile processing, and substrate compatibility, solution-processed colloidal quantum dots (CQDs) have recently gained significant attention and become one of the most competitive and promising candidates for optoelectronic devices. Among these CQDs, lead chalcogenide CQDs are getting very prominent and are widely investigated. In this paper, the recent progress of infrared (IR) photodetectors based on lead sulfide (PbS), lead selenide (PbSe), and ternary PbS x Se 1−x CQDs, and their underlying concepts, breakthroughs, and remaining challenges are reviewed, thus providing guidance for designing high-performance quantum-dot IR photodetectors.

PbE (E = S, Se) Colloidal Quantum Dot-Layered 2D Material Hybrid Photodetectors

“…A photoconductor is a two-contact optoelectronic device in which two ohmic source and drain electrodes are separated by a photoactive layer (i.e., a QD film; Figure 3A). Operated under an applied bias, photoconductors detect temporary changes in the carrier mobility, density, or both under incident illumination due to photogeneration of carriers in the photoactive layer [124]. Under a moderate field, the majority carriers (which can be either holes or electrons, depending on the material) have a higher mobility than the minority carriers.…”

“…Figures of merit [124,125,129] that account for device variables, such as device active area, response time, and spectral region are key for evaluating and comparing detector performance. The first measure of how effective a photodetector can be is how efficiently incident photons are Operation is similar to a photoconductor, but the device is fabricated on a substrate that allows for the possibility of applying a gate voltage [V G ] to tune transport in the photoactive area.…”

“…The responsivity [R(λ)] of a detector is a measure of the electrical signal output relative to the optical signal input, similar to the EQE. The units of R(λ) are amperes per watt [A/W] and it can be calculated by the following equation [124]:…”

“…Transit time can be calculated from the carrier mobility and bias voltage by τ transit = L 2 /(µV bias ) [130]. Noise equivalent power [NEP(λ)] is a measure of the detector sensitivity, defined as the optical power at which the signal-to-noise ratio (SNR) is 1, giving the minimum power the detector can effectively detect per square root of bandwidth [124], and is obtained using:…”

“…where A is the detector active area (cm 2 ). D*(λ) is proportional to R(λ), and it is also an indirect function of applied bias, temperature, modulation frequency, and wavelength [3,124]. When reporting D*(λ) the value should be accompanied by the measurement conditions to ensure that presented values are both correct and can be properly used for comparison of multiple devices.…”