Large current efficiency enhancement in the CsPbBr3 perovskite light-emitting diodes assisted by an ultrathin buffer layer

The solution-processed all-inorganic cesium lead halide perovskite material have attracted significant attention because of their high color purity, low cost, high thermal stability, high photoluminescence quantum yield. However, the low internal quantum efficiency immensely confine their application in display. In our work, we utilized an ultrathin buffer layer of the thermal activation delayed fluorescence (TADF) material 4,5-bis(carbazol-9-yl)− 1,2-dicyanobenzene (2CzPN), which can realize 100% internal quantum efficiency, to make an efficient Frster energy transfer for the energy of excitons on 2CzPN to be transferred to the excited state of CsPbBr₃. A CsPbBr₃ perovskite light-emitting diode (PeLED) with an optimized ultrathin 2CzPN buffer layer exhibited improved electroluminescence (EL) performance with lower turn on voltage of 3.6 V, the maximum luminance of 7660 cd/m², the maximum current efficiency of 2.83 cd/A, which are 7-fold and 5.5-fold compared to that of the conventional PeLED without the ultrathin buffer layer.