image: (a) PL spectrum of WLEDs based on CsPbBr3-OA QDs with a CRI of 82, (b) PL spectrum of WLEDs based on CsPbBr3-DA QDs with a CRI of 93 (The inset shows photographs of the devices without and with driving voltage.), and (c) CIE chromaticity diagram of both WLEDs。Figure 1a and 1b illustrate the spectra of CsPbBr3-OA QDs WLEDs and CsPbBr3-DA QDs WLEDs at a driving voltages of 2.65 V, respectively. Three emission peaks at 450, 520 and 610 nm have been observed, which are related to blue InGaN chip, CsPbBr3 QDs and AgInZnS QDs, respectively. The CIE color coordinates of (0.32, 0.35) and (0.44, 0.42) corresponding to the CsPbBr3-OA QDs and CsPbBr3-DA QDs WLEDs, respectively, as shown in Figure 1c. view more
Credit: OEA
In a new publication from Opto-Electronic Advances; DOI 10.29026/oea.2022.200075 , the research group of Professor Zhigang Zang from Chongqing University, Chongqing, China discusses realizing warm white light-emitting with high efficient emission and high color rendering index by using ligand modified CsPbBr3 quantum dots.
Nowadays, lighting accounts for approximately one-fifth of the global electricity consumption, which leads to a large increase in the emissions of carbon dioxide (CO2). To reduce the energy demand for lighting, solid-state white light-emitting diodes (WLEDs) are becoming the most promising illumination sources, which are much more efficient, energy savings and environmental friendliness than that of the traditional bulbs and fluorescent lighting sources. A common way of achieving a white light emission is composed of a near-UV or blue LEDs with a coating of either down-conversion materials (i.e. YAG:Ce3+ phosphors) or a combination of red and green phosphors. Unfortunately, such WLEDs suffer from poor white light performance after extensive use due to the different degradation rates between the blue LEDs and phosphors. In addition, they usually exhibit unsatisfactory high correlated color temperature (CCT) value and a low color rendering index (CRI <80) due to the facile absence of the red or green emission. In principle, an ideal white light emitting system needs the light source with an appropriate CCT between 2500 and 6500 K, and CRI above 80. Among the luminescent materials discovered so far, CsPbBr3 perovskite quantum dots (QDs) have been recognized as one of the most promising candidates for WLEDs due to the excellent optoelectronic properties.
The research group of Professor Zhigang Zang from Chongqing University presents a facile strategy to achieve excellent stability of CsPbBr3 QDs and high performance of WLEDs by using shorter 2-hexyldecanoic acid (DA) ligand to replace OA ligand for CsPbBr3 QDs. The ligand modified CsPbBr3 QDs exhibit a high PLQY of 96% with significantly enhanced stability, even when exposed to ethanol and water environments. Consequently, WLEDs by combining a blue InGaN LED with green ligand modified CsPbBr3 QDs and red AgInZnS QDs are achieved, which generate high quality warm white light emission
The WLEDs based on the modified CsPbBr3 QDs show a good thermal performance under high driving current, verifying their potential application in the field of solid-state lighting.
Article reference: Yan DD, Zhao SY, Zhang YB, Wang HX, Zang ZG. Highly efficient emission and high-CRI warm white light-emitting diodes from ligand-modified CsPbBr3 quantum dots. Opto-Electron Adv 5, 200075 (2022) . doi: 10.29026/oea.2022.200075
Keywords: CsPbBr3 quantum dots / ligand modification / stability / efficiency / white light-emitting diodes
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Professor Zhigang Zang received his PhD degree from Kyushu University in 2011. He joined the School of Optoelectronic Engineering, Chongqing University as a professor in 2014. He has made significant contribution to the synthesis of II-VI, III-V semiconductor materials and their applications in solar cells and light emitting diodes. He has published more than 104 scientific papers that have been widely cited by the scientific community (8000+ citations).
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