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

Rare earth(RE)ions,with abundant 4f energy level and unique electronic arrangement,are considered as substitutes for Pb^(2+)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(CsEuBr_(3) and CsEuCl_(3)).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.

Hot spots engineering by dielectric support for enhanced photocatalytic redox reactions

Regulating the surface plasmon resonance(SPR)of metallic nanostructures is of great interests for optical and catalytic applications,however,it is still a great challenge for tuning SPR features of small metallic nanoparticles(<10 nm).In this work,we design a unique dielectric support-urchin-like mesoporous silica nanoparticles(U-SiO_(2))with ordered long spikes on its surface,which can well enhance the SPR properties of~3 nm gold nanocrystals(AuNCs).The U-SiO_(2)not only realizes the uniform self-assembly of AuNCs,but also prevents their aggregation due to the unique confinement effect.The finite-difference time-domain simulations show that the AuNCs on U-SiO_(2)can generate plasmonic hot spots with highly enhanced electromagnetic field.Moreover,the hot electrons can be effectively and rapidly transferred through the interface junction to TiO_(2).Thus,a high visible-light-driven photocatalytic activity can be observed,which is 3.8 times higher than that of smooth photocatalysts.The concept of dielectric supports engineering provides a new strategy for tuning SPR of small metallic nanocrystals towards the development of advanced plasmon-based applications.

Metal cation substitution of halide perovskite nanocrystals

Recent years have seen a rapid development of lead halide perovskite(LHP)nanocrystals(NCs)as new and promising functional nanomaterials,which exhibit strong potential in a wide range of optoelectronic applications due to their superior properties and solution-processable advantages.However,to promote their progress in commercialization,overcoming the drawbacks of intrinsic lead toxicity and optimizing material performance are important and must be solved using alternative metal ions to replace Pb ions.In this review,we primarily summarize the recent development of lead-substitution strategies,which focus on the commonalities and differences of their functionalities that are induced by various doped ions.After a brief introduction to the synthesis,nucleation and growth of all-inorganic LHP NCs,a deep discussion of the crystalline structure,electronic band structure,defect states,exciton binding energy,exciton photodynamic process and stability is followed.Specifically,we highlight the importance of both theoretical calculations and experimental characterizations to establish indicative guidelines for high-performance semiconductor nanomaterials.Finally,the light emission applications are discussed,and several issues concerning future research on the controllable synthesis of halide perovskite NCs with low toxicity,superior reproducibility and properties are outlined.