| Affiliation: | 1. Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, 100083 China Shunde Innovation School, University of Science and Technology Beijing, Foshan, Guangdong, 528399 China;2. Key Laboratory of Automobile Materials Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130012 China;3. Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, 100083 China;4. Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083 China;5. Department of Physics and Astronomy and Photon Science Institute, University of Manchester, Manchester, M13 9PL UK;6. Department of Electronic and Information Engineering, Research Institute for Smart Energy (RISE), The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, 999077 China |
| Abstract: | Perovskite-based light-emitting diodes (PeLEDs) with a mixed halide composition can be used to obtain the “pure red” emission, i.e., in the 620–650 nm range, required for high-definition displays. However, fast halide ion migration induces phase separation in these materials under electric fields, resulting in poor spectral stability and low efficiency. Herein, a method for producing mixed halide CsPbI3-xBrx quantum dots (QDs) is reported in which ion migration is suppressed. The mixed halide composition is first achieved by anion exchange between CsPbI3 QDs and hydrobromic acid (HBr), during that the bromine ions efficiently passivate the iodine vacancies of the QDs. The original oleic acid ligands are then exchanged for 1-dodecanethiol (1-DT), which suppresses halide ion migration via the strong binding of the sulfhydryl group with the QD surface. PeLEDs based on these QDs exhibit a pure-red electroluminescence (EL) peak at 637 nm, a maximum external quantum efficiency (EQE) of 21.8% with an average value of 20.4%, a peak luminance of 2653 cd m−2, and low EQE decease with increasing luminance. The EL spectrum of these devices is stable even at 6.7 V and they have an EQE half-life of 70 min at an initial luminance of 150 cd m−2. |
