Efficient and Color-Tunable Quasi-2D CsPbBr_<i>x</i>Cl_3–<i>x</i> Perovskite\nBlue Light-Emitting Diodes

Abstract

Metal halide perovskites\nare emerging as promising candidate materials for light-emitting diodes\n(LEDs) due to their high luminescence, color purity, tunable bandgaps,\nand solution processabilities. In the past several years, the metal\nhalide perovskite based LEDs (PeLEDs) in the green and red light spectral\nrange have been demonstrated in high brightness and good efficiency.\nHowever, the performance of blue PeLED is still limited by the low\nblue light emission efficiency of present metal halide perovskite\nmaterials. Here, we report a facile solution method to fabricate a\nseries of quasi-2D CsPbBr_<i>x</i>Cl_3–<i>x</i> perovskite films with high photoluminescent quantum\nyields (PLQYs) in the blue light spectral range. By compositional\nengineering via increasing the content of chloride, we achieved the\ntunable light emission wavelength of quasi-2D CsPbBr_<i>x</i>Cl_3–<i>x</i> perovskite films from\ngreen (504 nm) to blue (470 nm) with a high PLQY up to 42% at 486\nnm. In addition, we developed a novel NiO_<i>x</i>/LiF hole transport layer with high affinity to precursor solution\nfor improving the film quality of quasi-2D CsPbBr_<i>x</i>Cl_3‑x perovskite while reducing the quenching\neffect of hole transport layer to as-formed perovskite film. As a\nresult, the blue PeLEDs based on quasi-2D CsPbBr_<i>x</i>Cl_3‑x perovskite films show color-tunable\nemissions and the external quantum efficiency of 0.52% as well as\nhigh brightness of 1446 cd m^–2 are achieved at 490\nnm.