强共价低声子能量稀土硫化物:破解Cr3+短波红外发光效率与稳定性难题OA

Phosphor-converted light-emitting diodes(pc-LEDs)based on a"blue GaN chip+short-wave infrared(SWIR)phosphor"architecture offer several advantages,including compact size,low power consumption,broad emis-sion spectra,low cost,and ease of integration.They are therefore regarded as an important technological route toward portable and intelligent SWIR light sources.However,as the emission wavelength is further red-shifted from the near-infrared region to the SWIR region,phosphor materials typically suffer from significantly enhanced multiphonon nonra-diative relaxation,leading to reduced external quantum efficiency,deteriorated thermal stability,and insufficient de-vice output power.Recently,Li et al.reported a class of highly efficient Cr3+-doped ternary rare-earth sulfide phos-phors,NaLnS2:Cr3+(Ln=Lu,Y,Gd).This study proposes and validates a new paradigm for SWIR luminescence that differs from the conventional crystal-field engineering strategy used in oxide phosphors.Specifically,the strong covalen-cy of the sulfide host induces a pronounced nephelauxetic effect,reducing the effective electron-electron repulsion of Cr3+3d electrons and decreasing the energy separation between the 4T2 excited state and the 4A2 ground state,while the low phonon energy and weak electron-phonon coupling of the sulfide lattice suppress nonradiative losses.This synergis-tic mechanism overcomes the long-standing challenge in Cr3+-doped SWIR phosphors,where long-wavelength emission,high efficiency,and excellent thermal stability have traditionally been difficult to achieve simultaneously.