Effects of Tellurium Doping on Environmental Stability and Luminous Performance of CsPbBr₃ Quantum Dots

The effects of elemental tellurium doping and decorating on the photoluminescence quantum yield (PL QY) and the environmental stability of the CsPbBr₃ quantum dots (QDs) have been systematically studied. The PL spectra blue-shifts from 520 to 464 nm gradually with the increase in the amount of Te, and the full width at half-maximum (FWHM) increases from 20 to 62 nm and decreases to 27 nm accordingly. The morphology of the untreated samples has a rectangular shape with distinct boundaries, whereas the Te-doped samples have a semi-core-shell structure with partially coated CsPb₂Br₅ after tellurium doping. Furthermore, the apparent size of the nanocomposites increases to 20 nm, but the crystal size of the core decreases slightly according to the broadened peaks of X-ray diffraction (XRD). Further investigation by X-ray photoelectron spectroscopy shows that the binding energy of Pb-Br increases and Pb-Te bonds are formed in Te-doped samples, which can enhance the stability of QDs from the view of strengthening the chemical bonds and inhibiting the detaching behavior of bromine under moisture. At the nominal content of Pb/Te = 1:0.4, the thermal decomposition temperature of the QDs increases from 300 to 500 °C; the maximum of PL QY increases to 70% for the 1:0.4 sample and the relative PL peak intensity maintains 50% of the initial value after a 60 h aging simulation. Finally, the nanocomposite materials are fabricated into a white light-emitting device (WLED). Under the illumination of a commercial GaN chip, the device shows a good Commission Internationale de lEclairage (CIE) color coordination of (0.3291,0.3318).