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[ Instrument R&D of Instrument Network ] Since the concept of up-converted circularly polarized luminescence (UC-CPL) has been proposed, UC-CPL based on different luminescence mechanisms has been reported one by one and attracted widespread attention. At present, the resulting luminescence asymmetry factor (glum) is generally low. Looking for a method that can improve the UC-CPL luminescence asymmetry factor and have good luminous efficiency has become an important issue in the field of up-converting circularly polarized luminescence. .
Recently, the team of Duan Pengfei, a researcher at the National Nanoscience Center of the Chinese Academy of Sciences, discovered that upconversion nanoparticles (UCNPs) and perovskite nanocrystals (CsPbBr3) were dispersed into chiral nematic liquid crystals (N*LC) through energy transfer between particles. The process can achieve up-converted circularly polarized luminescence with a glum value of up to 1.1. In this process, the emission of CsPbBr3 is located exactly in the center of the photonic band gap, so the up-converted circularly polarized light obtained has a high glum value. The luminescence of UCNPs is enhanced due to being at the edge of the photonic band gap, and can further enhance the luminescence of CsPbBr3 through the process of radiant energy transfer. This design overcomes the suppression of luminescence at the center of the photonic band gap, making CsPbBr3's up-converting circularly polarized luminescence have a high luminous intensity while having a high glum value. In addition, the up-conversion circularly polarized luminescence and energy transfer processes of CsPbBr3 can be controlled by electric fields and external forces. Related research results were published in Advanced Materials (Adv. Mater. 2020, 32, 2000820).
In recent years, Duan Pengfei’s research team has made progress in the construction of highly efficient circularly polarized luminescent materials, and has achieved various photophysical processes to directly control the excited state chirality of luminescent substances, thereby developing a variety of methods for modulating the CPL luminescence properties. Recently, the research team published a new perspectives to trigger and modulate circularly polarized luminescence of complex and aggregated systems: energy transfer, photon upconversion, charge transfer in Accounts of Chemical Research (2020, DOI: 10.1021/acs.accounts.0c00112). , and organic radical's review article summarizes and looks forward to the research work of the research team on the photophysical control of the circularly polarized light emission process in recent years. Energy transfer, photon frequency up-conversion based on triplet-triplet annihilation, intermolecular charge transfer and organic radical emission, etc., these photophysical processes can affect the chirality of singlet, double and triplet excited states. Through the regulation of these photophysical processes, a significant amplification of the circularly polarized light asymmetry factor can be achieved. The direct control of the excited state of the chiral system through the photophysical process provides a new research perspective for understanding and adjusting the properties of CPL, and will help to develop intelligent chiral optical materials.
The research work was supported by the National Natural Science Foundation of China, the Strategic Leading Science and Technology Project of the Chinese Academy of Sciences (Category B), and the Ministry of Science and Technology's key R&D plan.