Ultrapure and highly efficient green light emitting devices based on ligand-modified CsPbBr₃ quantum dots

All inorganic CsPbBr 3 perovskite quantum dots (QDs) have been recognized as promising optical materials to fabricate green light emission devices because of their excellent optical performance. However, regular CsPbBr 3 QDs with an oleic acid (OA) ligand show poor stability, which limits their practical application. We replaced the OA ligand in CsPbBr 3 QDs with a 2-hexyldecanoic acid (DA) ligand and, in the synthesis, found that the new material has better optical properties than regular CsPbBr 3 QDs ( CsPbBr 3 - OA QDs). Due to the strong binding energy between the DA ligand and QDs, the ligand-modified CsPbBr 3 QDs ( CsPbBr 3 - DA QDs) show a high photoluminescence quantum yield (PLQY) of 96%, while the PLQY of CsPbBr 3 - OA QDs is 84%. Subsequently, the CsPbBr 3 QDs coated on the blue light-emitting diode (LED) chips as green phosphors are demonstrated. The color conversion from blue to pure green is achieved by adding the CsPbBr 3 - OA QDs solution up to 60 μL, while the pure green emission devices only need 18 μL CsPbBr 3 - DA QDs solution under the same concentration. The ultrapure, highly efficient green light-emitting devices based on CsPbBr 3 - DA QDs exhibit a luminous efficiency of 43.6 lm/W with a CIE (0.2086, 0.7635) under a 15.3 mA driving current. In addition, the green emission wavelength of the devices based on CsPbBr 3 - DA QDs almost has no shift, even under a high injection current. These results highlight the promise of DA ligand-modified CsPbBr 3 QDs for light-emitting devices and enrich the application field of ligand-modified CsPbBr 3 QDs.