Abstract
Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. However, mixed halide perovskites usually suffer from phase segregation under electrical biases. Herein, we obtain high-performance and color-stable blue perovskite LEDs (PeLEDs) based on mixed bromide/chloride three-dimensional (3D) structures. We demonstrate that the color instability of CsPb(Br1–xClx)3 PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br1–xClx)3 PeLEDs, with maximum external quantum efficiencies of up to 4.5% and high luminance of up to 5351 cd m–2 in the sky-blue region (489 nm). Our work provides new insights into the color instability issue of mixed halide perovskites and can spur new development of high-performance and color-stable blue PeLEDs.
Highlights
Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites
One approach for blue perovskite LEDs (PeLEDs) is to develop quantumconfined structures based on pure bromide perovskites; for instance, mixed-dimensional perovskites and perovskite quantum dots (QDs) have been developed.[11−13] These quantum-confined structures incorporate long-chain organic ligands to suppress the growth of perovskite crystals, keeping at least one direction of the crystals in the range of their Bohr diameters to increase the bandgap.[14−16] it is rather difficult to realize uniform quantum confinement; for instance, multiple phases exist in mixed-dimensional perovskites, sometimes even leading to broad emission and limiting the color purity.[17]
We report color-stable blue PeLEDs with additive incorporation into mixed Br/Cl 3D perovskites; this additive is found efficient in passivating the surface defects at grain boundaries, which effectively blocks the ion migration channels to eliminate the color instability of CsPb(Br1−xClx)[3] PeLEDs
Summary
Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. We report color-stable blue PeLEDs with additive incorporation into mixed Br/Cl 3D perovskites; this additive is found efficient in passivating the surface defects at grain boundaries, which effectively blocks the ion migration channels to eliminate the color instability of CsPb(Br1−xClx)[3] PeLEDs. The optimized device with sky-blue emission peaking at 489 nm delivers a peak EQE of 4.5% and a maximum luminance of 5351 cd m−2; these values are 2.9% and 2240 cd m−2 for the device with electroluminescence (EL) peaking at 478 nm.
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