Gaozhao Chen, Xiong Shen, He Liu, Wentao Hao, Qiuyun Ouyang
The composites of CsPb(Cl/Br) 3 incorporating carbon quantum dots (CQDs) were prepared via a thermal injection method. Enhanced-stability CsPb(Cl/Br) 3 @CQDs@TiO 2 composites were fabricated from CsPb(Cl/Br) 3 @CQDs precursors through tetrabutyl titanate hydrolysis. The transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses confirm the successful formation of a TiO 2 coating on the composite. The transient photoluminescence (TRPL) measurements reveal lifetimes of 3.89, 4.2, and 2.3 ns for CsPb(Cl/Br) 3, CsPb(Cl/Br) 3 @CQDs, and CsPb(Cl/Br) 3 @CQDs@TiO 2, respectively. The increased lifetime in CsPb(Cl/Br) 3 @CQDs suggests that CQDs may contribute to surface passivation of CsPb(Cl/Br) 3, suppressing nonradiative recombination. The shortened lifetime observed after TiO 2 coating indicates further modification of interfacial carrier relaxation dynamics. Temperature-dependent PL analysis shows that CsPb(Cl/Br) 3 @CQDs@TiO 2 exhibits a higher exciton binding energy (65.7 meV) compared with CsPb(Cl/Br) 3 @CQDs (36.2 meV), indicating an enhanced excitonic state in the TiO 2 -coated composite structure. The electrochemical impedance spectroscopy (EIS) and photocurrent measurements indicate reduced charge transfer resistance and enhanced photocurrent density (0.6 μA cm –2 ), consistent with improved interfacial carrier transport. The environmental stability tests further confirm that CsPb(Cl/Br) 3 @CQDs@TiO 2 exhibits significantly improved stability compared with CsPb(Cl/Br) 3 @CQDs. These results highlight the synergistic roles of CQD-induced passivation and TiO 2 interfacial engineering in modulating interfacial carrier behavior, leading to improved optoelectronic performance and environmental stability.