Objective In quantum communication, achieving efficient transmission and long-distance- distance communication relies on an ideal single- photon source. CsPbBr3 3 quantum dots hold significant promise as single- photon sources due to their high probability of single- photon emission. Among the methods to enhance CsPbBr3 3 quantum dots' single- photon performance, size reduction is crucial. In this study, we synthesize CsPbBr3 3 quantum dots doped with varying concentrations of Al3+ 3+ ions using a thermal injection method and systematically investigate their optical and material properties. The results demonstrate that Al3+ 3+ ion doping effectively modulates the emission intensity and wavelength of CsPbBr3 3 quantum dots while enhancing the interaction of Pb-Br bonds, thus significantly improving their environmental stability. Moreover, by leveraging the smaller ionic radius of Al3+ 3+ ions compared to Pb2+ 2+ ions, Al3+ 3+ ion doping effectively induces lattice contraction in CsPbBr3 3 quantum dots, leading to reduced size and enhanced size uniformity. Consequently, the reduced size enhances the quantum confinement effect, significantly improving single- photon emission performance. This study presents new strategies for optimizing perovskite quantum dot single- photon sources, advancing the development of perovskite single- photon sources. Methods We utilize a hot injection method to synthesize CsPbBr3 3 quantum dots and Al3+-doped 3+- doped CsPbBr3 3 quantum dots, ensuring high crystallinity and superior size uniformity. The method involves two steps. First, a mixture of cesium carbonate, oleic acid, and octadecene is heated for 2 h in an inert environment. To enhance the synthesis quality of quantum dots, an excess of oleic acid is added, resulting in a cesium oleate precursor that is soluble at room temperature. Second, a mixture of lead bromide, aluminum bromide, oleic acid, oleylamine, and octadecene is heated for 2 h in an inert environment. This is followed by the rapid injection of 0.4 mL of cesium oleate precursor. After allowing the reaction to proceed for 5 s, immediate cooling is achieved using an ice- water bath. Subsequently, well- dispersed quantum dot solutions are obtained through high-speed- speed centrifugation. Throughout the synthesis process, quantum dots with different doping concentrations (Al/Pb molar ratios of 0:1, 1:2, 1:1, 2:3, and 3:2) are synthesized by controlling the amount of aluminum bromide added. Results and Discussions The prepared Al:CsPbBr3 3 quantum dots can maintain the crystal structure of CsPbBr3 3 quantum dots within a specific concentration range of Al3+ 3+ ions, successfully introducing the energy level of Al3+ 3+ ions. The addition of Al3+ 3+ ions enhances the interaction of Pb-Br bonds in CsPbBr3 3 quantum dots and significantly improves their stability (Fig. 2). Notably, while maintaining the crystal morphology of CsPbBr3 3 quantum dots, Al:CsPbBr3 3 quantum dots exhibit reduced size and improved size uniformity. This is due to the substitution of larger Pb2+ 2+ ions by smaller Al3+ 3+ ions (Fig. 3). Furthermore, fluorescence and absorption spectral analysis reveals that Al3+ 3+ ions effectively enhance the optical properties of CsPbBr3 3 quantum dots, significantly increasing their fluorescence intensity. Importantly, CsPbBr3 3 quantum dots and Al:CsPbBr3 3 quantum dots exhibit the same emission linewidth and demonstrate good environmental stability (Fig. 5). These improvements broaden the potential applications of Al:CsPbBr3 3 quantum dots across various fields. Conclusions In the paper, we successfully prepare Al:CsPbBr3 3 quantum dots using a hot injection method and comprehensively investigate the influence of Al3+ 3+ ions on the properties of CsPbBr3 3 quantum dots. The results from fluorescence spectra and absorption spectra indicate an effective enhancement in the fluorescence intensity of the quantum dots. With an increasing Al/Pb ratio, both the fluorescence and absorption spectra of the quantum dots exhibit a blue shift. However, when the Al/Pb ratio reaches 3:2, the emission and absorption wavelengths unexpectedly undergo a red shift. Combined with X-ray- ray diffractometer (XRD) data, this suggests that while a small amount of Al3+ 3+ ions improves the optical properties of CsPbBr3 3 quantum dots, an excessive amount disrupts their crystal structure. X-ray- ray photoelectron spectroscopy (XPS) data demonstrate that the introduction of Al3+ 3+ ions shifts the Pb and Br energy levels of CsPbBr3 3 quantum dots towards higher binding energies, enhancing Pb-Br bond interaction and thereby improving stability. Moreover, single quantum dot excitation tests comparing CsPbBr3 3 quantum dots and Al:CsPbBr3 3 quantum dots (Al/Pb molar ratio of 1: 1) reveal distinct fluorescence blinking characteristics. The g 2 (0) values suggest that Al: CsPbBr3 3 quantum dots (Al/Pb molar ratio of 1:1) demonstrate superior single- photon performance, attributed to the effective reduction in quantum dot size, improved size uniformity, and enhanced quantum confinement effects upon the introduction of Al3+ 3+ ions. This study offers new experimental insights and methods for the preparation of perovskite quantum dots and the optimization of their quantum light source performance.
