Size-Dependent Thermal Activation Emissions in Infrared PbS Colloidal Quantum Dots

The PbS colloidal quantum dots (CQDs), with the advantages of a strong quantum confinement effect and broad range adjustable in photoluminescence, have been paid much attention because of their great potential applications in the field of infrared optoelectronics. Therefore, it is of great significance to investigate their photoluminescence properties. In this study, three PbS CQDs are fabricated by the thermal injection method, and their sizes are adjusted from 3.8 to 5.1 nm by controlling the growth duration. Their room-temperature PL spectra are centered at 1323, 1341, and 1440 nm. The temperature- and power-dependent PL spectra are further investigated to reveal the emission mechanism. The peak positions have a distinct blue shift with an increasing temperature. Meanwhile, a thermal activation phenomenon is observed in the PbS CQDs with sizes of 3.8 and 4.4 nm, which is attributed to the size-dependent quantum confinement effect and electron-phonon interaction. This work has a great influence on the adjustment of the optical properties of PbS CQDs.