Enhancing optical properties and stability of cesium lead halide quantum dots through nickel substitution and ligand change

In this study, we investigated the methods for prolonged lifetime in the CsPbX3 (X: Cl, Br, I) structured perovskite materials. First, the changes in structural and optical properties were compared by doping Ni in the CsPbBr3 quantum dots (QDs). The steady-state photoluminescence (PL) intensity of Ni-doped QDs shows 3.8 times increase comparing with undoped QDs. CsPbBr3 without nickel had a quantum efficiency of only 56.7 %, whereas CsPbBr3 doped with nickel had a quantum efficiency of 82.9 %. It was found that the doped divalent element acts as a defect in the perovskite structure, reducing the recombination rate of electrons and holes. After 48 hours UV-light irradiation, PL intensity of CsPbBr3 decreased about 70 % while that of Ni-substituted CsPbBr3 QDs decreased only 18 %, indicating the prolonged stability against UV-light irradiation. Furthermore, Ni-substituted CsPbBr3 QDs shows higher stability against temperature and moisture. These results confirmed that Ni substitution method is effective to increase the stability of CsPbX3 QDs. Second, we used sulfuroleylamine (S-OLA) complex which was utilized to etch the defect-rich surface of the CsPbI3 QDs and then self-assembly to form a matrix outside the CsPbI3 QDs protected the QDs from environmental moisture and solar irradiation. The PL intensity of the CsPbI3 QDs increased by 21% of its initial value. There was a significant increase in the colloidal stability of the CsPbI3 QDs. The introduction of S-OLA induced the recovery of the lost photoluminescence of the nonluminous aged CsPbI3 QDs with time to 95% of that of the fresh QDs. Furthermore, the PL was maintained for one month. The increase in the stability and PL intensity are critical for realizing high-performance perovskite-QD-based devices. In this study, we investigated the methods for prolonged lifetime in the CsPbX3 (X: Cl, Br, I) structured perovskite materials. First, the changes in structural and optical properties were compared by doping Ni in the CsPbBr3 quantum dots (QDs). It was found that the doped divalent element acts as a defect in the perovskite structure, reducing the recombination rate of electrons and holes. Ni-substituted CsPbBr3 QDs shows higher stability against temperature and moisture. These results confirmed that Ni substitution method is effective to increase the stability of CsPbX3 QDs. Second, we used sulfuroleylamine (S-OLA) complex which was utilized to etch the defect-rich surface of the CsPbI3 QDs and then self-assembly to form a matrix outside the CsPbI3 QDs protected the QDs from environmental moisture and solar irradiation. The introduction of S-OLA induced the recovery of the lost photoluminescence of the nonluminous aged CsPbI3 QDs with time to 95% of that of the fresh QDs.