A Comprehensive Review on Mechanisms and Applications of Rare‐Earth Based Perovskite Nanocrystals†

Comprehensive Summary Rare earth (RE) ions, with abundant 4f energy level and unique electronic arrangement, are considered as substitutes for Pb2+ in perovskite nanocrystals (PNCs), allowing for partial or complete replacement of lead and minimizing environmental impact. This review provides a comprehensive overview of the characteristics of RE‐doped PNCs, including up‐conversion luminescence, down‐conversion luminescence, and quantum confinement effects, etc. Additionally, RE doping has been found to effectively suppress defect formation, reduce nonradiative recombination, enhance photoluminescence quantum yield (PLQY), and even allow for controlling over the morphology of the nanocrystals. The review also highlights the recent advancements in lead‐free RE‐based perovskites, especially in the case of Eu‐based perovskites (CsEuBr3 and CsEuCl3). Furthermore, it briefly introduces the applications of PNCs in various fields, such as perovskite solar cells (PSCs), luminescent solar concentrators (LSCs), photodetectors (PDs), and light‐emitting diodes (LEDs). A systematic discussion on the luminescence mechanisms of RE‐doped PNCs and lead‐free RE‐based perovskites is provided, along with an outlook on future research directions. The ultimate goal of this review is to provide guidance for the development of RE‐based perovskite optoelectronic devices. Key Scientists In 2015, Kovalenko et al. pioneered the synthesis of lead‐based perovskite nanocrystals using the thermal injection method. Concurrently, Zhong et al. introduced the ligand‐assisted reprecipitation method. These methods have become the predominant approaches for fabricating lead‐based perovskite nanocrystals. In 2017, Song et al. successfully incorporated various rare earth ions (Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, and Yb3+) into CsPbCl3 perovskite nanocrystals. They also observed the quantum cutting effect induced by defect states, facilitated by the doping of Yb3+. Gamelin et al. subsequently proposed that CsPbCl3:Yb3+ nanocrystals exhibit quantum cutting effects due to the introduction of charge‐compensating defects (VPb), resulting in the formation of Yb3+‐VPb‐Yb3+ defect complexes with shallow defect levels. In 2020, Zhang et al. successfully doped Nd3+ into CsPbBr3, yielding blue luminescent nanocrystals with a central wavelength of 459 nm and up to 90% photo‐luminescence quantum yield (PLQY). In the same year, Yang et al. achieved the synthesis of pure phase CsEuCl3 perovskite nanocrystals for the first time. In 2022, Paik et al. synthesized Cs3LnCl6 (Ln = Y, Ce, Gd, Er, Tm, Yb, Eu, Tb) nanocrystals using the thermal injection method. In 2023, Zhang et al. successfully introduced Ni2+ doping into CsEuCl3, enhancing the PLQY of CsEuCl3 nanocrystals from 5% to 19.7%. This review focuses on the development history of perovskite nanocrystals, including rare earth‐doped lead‐based perovskite nanocrystals and rare earth‐based lead‐free perovskite nanocrystals, as well as their applications.