Extended wavelength and enhanced sensitivity of PbS colloidal quantum dots/Bi₂Te₃ photodetector by band alignment engineering

The tunable band gap of PbS colloidal quantum dots (CQDs) from ultraviolet (UV) to short-wave infrared (SWIR) bands provides many potential applications in optoelectronics. However, synthesis of large-sized CQDs that exhibit good stability and sensitivity for extended wavelength still remains a technological challenge. In this paper, a novel broadband photodetector based on small size PbS CQDs (with exciton absorption peak at 927 nm) and Bi₂Te₃ (with wide spectral sensitivity and high absorption) was developed and studied. The device, which comprised of ITO/AZO/PbS CQDs/Bi₂Te₃/Al, provided an excellent band alignment that facilitated charge dissociation and transmission hence improving the device sensitivity. Furthermore, wavelength extension was also realized through the synergistic effect of these materials, thus demonstrating broadband photodetection with high sensitivity. The heterostructure photodetector demonstrated good performance in the visible and near infrared ranges, especially at a wavelength of 1050 nm exhibiting a high responsivity (R) and detectivity (D*) of 161 A/W and 3.2 × 10¹³ Jones, respectively. In addition, the device exhibited excellent stability and reversibility after one month of storage without any encapsulation. This work lays a good foundation for the construction of the next generation of highly sensitive broadband CQDs photodetectors.