| Recently,all-inorganic halide perovskite nanocrystals(NCs)have demonstrated highly efficient luminescence in the whole visible spectral range and shown great potential applications in optoelectronic devices.However,the surface of highly luminescent NCs is often protected by long-chain organic ligands.These NCs wrapped by organic ligands show poor carrier transport performance,which directly leads to the difficulty in achieving high-performance photoelectric devices.To solve this problem,previous work was limited to the use of short-chain ligand-exchange strategy.Due to the ionic nature of perovskite materials,this strategy usually leads to changes in the morphology and optical properties of NCs.Therefore,it is necessary to find an effective ligand exchange strategy to obtain all-inorganic halide perovskite NCs with high luminescence efficiency,stable morphology and few surface organic ligands,so as to realize halide perovskite optoelectronic devices with excellent performance.In addition,the application of halide perovskite materials in photoelectric devices has made a great breakthrough,especially in the field of perovskite light-emitting diodes(LEDs).The external quantum efficiency(EQE)of monochromatic halide perovskite LED has been comparable to that of commercial LED.However,it is difficult to realize white-light LEDs using a single perovskite active layer.To further promote the application of halide perovskite materials in the field of display and lighting,it is urgent to develop a new strategy to realize halide perovskite white LEDBased on the above two scientific issues,this paper conducts the following research:1)Based on the mild chemical reaction between thionyl halide(SOX2)and surface ligands of cesium tin halide(CsPbX3,X=Cl,Br,I)NCs,a general inorganic ligand exchange strategy was proposed.The halide perovskite NCs with high luminescence efficiency,good morphology and almost no organic ligands on the surface were obtained.Finally,we applied the CsPb(Cl/Br)3 NCs featuring ligand-lacking surface to LED,and the blue LED to obtain a maximum EQE of 1.35%and an electroluminescence(EL)peak at 460 nm.This work provides a new way for the preparation of high-quality halide perovskite NCs with few organic ligands and lays a foundation for the application of halide perovskite NCs in optoelectronic devices.2)A new architecture featuring "island" structure of perovskite NCs films is proposed to effectively prevent the ion migration in mixed-halide perovskite LED.It is found that the organic carrier-transport materials filled with the gap between the "islands" have the function of sharing current and voltage,which greatly improves the stability of the mixed halide perovskite LED.Combining the yellow light emitting interfacial exciplex produced by the organic transport material filled in the gap between "islands" with stably blue-emitting CsPb(Cl/Br)3 NCs enables us to achieve a white LED with a single perovskite layer.The white LED to obtain a maximum EQE of 1.06%while achieving pure white emission with color coordinates of(0.33,0.33).This work not only solves the problem of halogen separation in mixed halide perovskite LED,but also provides an innovative strategy for obtaining halide perovskite-based white LED. |
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