Efficient and bright broadband electroluminescence based on environmentfriendly metal halide nanoclusters

Broadband electroluminescence based on environment-friendly emitters is promising for healthy lighting yet remains an unprecedented challenge to progress.The copper halide-based emitters are competitive candidates for broadband emission,but their high-performance electroluminescence shows inadequate broad emission bandwidth of less than 90 nm.Here,we demonstrate efficient ultra-broadband electroluminescence from a copper halide(CuI)nanocluster single emitter prepared by a one-step solution synthesis-deposition process,through dedicated design of ligands and subtle selection of solvents.The CuI nanocluster exhibits high rigidity in the excitation state as well as dual-emissive modes of phosphorescence and temperature-activated delayed fluorescence,enabling the uniform cluster-composed film to show excellent stability and high photoluminescent efficiency.In consequence,ultra-broadband light-emitting diodes(LEDs)present nearly identical performance in an inert or air atmosphere without encapsulation and outstanding high-temperature operation performance,reaching an emission full width at half maximum(FWHM)of~120 nm,a peak external quantum efficiency of 13%,a record maximum luminance of~50,000 cd m^(−2),and an operating half-lifetime of 137 h at 100 cd m^(−2).The results highlight the potential of copper halide nanoclusters for next-generation healthy lighting.

Surface and intrinsic contributions to extinction properties of ZnSe quantum dots

This work studies extinction properties of ZnSe quantum dots terminated with either Se-surface or Zn-surface(Se-ZnSe or Zn-ZnSe QDs).In addition to commonly observed photoluminescence quenching by anionic surface sites,Se-ZnSe QDs are found to show drastic signatures of Se-surface states in their UV-visible(Vis)absorption spectra.Similar to most QDs reported in literature,monodisperse Zn-ZnSe QDs show sharp absorption features and blue-shifted yet steep absorption edge respect to the bulk bandgap.However,for monodisperse Se-ZnSe QDs,all absorption features are smeared and a low-energy tail is identified to extend to an energy window below the bulk ZnSe bandgap.Along increasing their size,a cyclic growth of ZnSe QDs switches their surface from Zn-terminated to Se-terminated ones,which confirms that the specific absorption signatures are reproducibly repeated between those of two types of the QDs.Though the extinction coefficients per unit of Se-ZnSe QDs are always larger than those of Zn-ZnSe QDs with the same size,both of them approach the same bulk limit.In addition to contribution of the lattice,extinction coefficients per nanocrystal of Zn-ZnSe QDs show an exponential term against their sizes,which is expected for quantum-confinement enhancement of electron-hole wavefunction overlapping.For Se-ZnSe QDs,there is the third term identified for their extinction coefficients per nanocrystal,which is proportional to the square of size of the QDs and consistent with surface contribution.