The development of efficient perovskite light-emitting diodes(PeLEDs)relies strongly on the fabrication of perovskite films with rationally designed structures(grain size,composition,surface,etc.).Therefore,an underst...The development of efficient perovskite light-emitting diodes(PeLEDs)relies strongly on the fabrication of perovskite films with rationally designed structures(grain size,composition,surface,etc.).Therefore,an understanding of structure-performance relationships is of vital importance for developing high-performance perovskite devices,particularly for devices with in-situ fabricated perovskite nanocrystal films.In this study,we reveal the vertical structure of an in-situ fabricated quasi-two-dimensional perovskite film.By combining time-of-flight secondary ion mass spectrometry,energy dispersive spectroscopy,grazing incidence wide-angle X-ray scattering(GIWAXS),and low-temperature photoluminescence spectra,we illustrate that the resulting in-situ fabricated DPPA_(2)Cs_(n-1)Pb_(n)(Br_(0.3)I_(0.7))_(3n+1)(DPPA^(+):3,3-diphenylpropylammonium)film has a gradient structure with a very thin layer of ligands on the surface,predominantly small-n domains at the top,and predominantly large-n domains at the bottom owing to the solubility difference of the precursors.In addition,GIWAXS measurements show that the domain of n=2 on the top layer has an ordered in-plane alignment.Based on the understanding of the film structure,we developed an in-situ fabrication process with ligand exchange to achieve efficient pure red PeLEDs at 638 nm with an average external quantum efficiency(EQE)of 7.4%.The optimized device had a maximum luminance of 623 cd/m^(2) with a peak EQE of 9.7%.展开更多
Biexciton emission in quantum dots is an efficient way to generate entangled photon pairs,which are key resources in quantum informatics.Compared with epitaxial grown quantum dots,chemically synthesized colloidal quan...Biexciton emission in quantum dots is an efficient way to generate entangled photon pairs,which are key resources in quantum informatics.Compared with epitaxial grown quantum dots,chemically synthesized colloidal quantum dots show advantages of tunable wavelength and easy integration to realize quantum light sources.However,biexciton efficiency of colloidal quantum dots has been limited by Auger recombination.In this paper,we reported nonlocal interaction enhanced biexciton emission with efficiency up to 80% in large perovskite nanocrystals(>20 nm).The nonlocal interaction between carriers and excitons leads to the abnormal exponential decrease of Auger recombination with volume in large nanocrystals,which distinguishes with the linear scaling in small counterparts.Such an exponential decrease of Auger recombination results in long lifetime of biexcitons,responsible for the required high biexciton efficiency.The discovery of nonlocal effects in large semiconductor nanocrystals provides new strategies to achieve high efficiency multiple excitons for quantum optics and energy conversation applications.展开更多
基金supported by the National Natural Science Foundation of China(61735004).
文摘The development of efficient perovskite light-emitting diodes(PeLEDs)relies strongly on the fabrication of perovskite films with rationally designed structures(grain size,composition,surface,etc.).Therefore,an understanding of structure-performance relationships is of vital importance for developing high-performance perovskite devices,particularly for devices with in-situ fabricated perovskite nanocrystal films.In this study,we reveal the vertical structure of an in-situ fabricated quasi-two-dimensional perovskite film.By combining time-of-flight secondary ion mass spectrometry,energy dispersive spectroscopy,grazing incidence wide-angle X-ray scattering(GIWAXS),and low-temperature photoluminescence spectra,we illustrate that the resulting in-situ fabricated DPPA_(2)Cs_(n-1)Pb_(n)(Br_(0.3)I_(0.7))_(3n+1)(DPPA^(+):3,3-diphenylpropylammonium)film has a gradient structure with a very thin layer of ligands on the surface,predominantly small-n domains at the top,and predominantly large-n domains at the bottom owing to the solubility difference of the precursors.In addition,GIWAXS measurements show that the domain of n=2 on the top layer has an ordered in-plane alignment.Based on the understanding of the film structure,we developed an in-situ fabrication process with ligand exchange to achieve efficient pure red PeLEDs at 638 nm with an average external quantum efficiency(EQE)of 7.4%.The optimized device had a maximum luminance of 623 cd/m^(2) with a peak EQE of 9.7%.
基金supported by Beijing Natural Science Foundation(Z210018,H.Z.)National Natural Science Foundation of China(12074037,Y.Z.).
文摘Biexciton emission in quantum dots is an efficient way to generate entangled photon pairs,which are key resources in quantum informatics.Compared with epitaxial grown quantum dots,chemically synthesized colloidal quantum dots show advantages of tunable wavelength and easy integration to realize quantum light sources.However,biexciton efficiency of colloidal quantum dots has been limited by Auger recombination.In this paper,we reported nonlocal interaction enhanced biexciton emission with efficiency up to 80% in large perovskite nanocrystals(>20 nm).The nonlocal interaction between carriers and excitons leads to the abnormal exponential decrease of Auger recombination with volume in large nanocrystals,which distinguishes with the linear scaling in small counterparts.Such an exponential decrease of Auger recombination results in long lifetime of biexcitons,responsible for the required high biexciton efficiency.The discovery of nonlocal effects in large semiconductor nanocrystals provides new strategies to achieve high efficiency multiple excitons for quantum optics and energy conversation applications.