Color-Stable Blue Light-Emitting Diodes Enabled by Effective Passivation of Mixed Halide Perovskites

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(Br 1– x Cl x ) 3 PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br 1– x Cl x ) 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.

Ion Migration in Perovskite Light‐Emitting Diodes: Mechanism, Characterizations, and Material and Device Engineering

“…Similarly, the emissions of the 3D blue emitter CsPbBr x Cl 3-x became gradually red-shifted and broadened during the device's operation. [116,159,165,168,169] It is worth noting that for blue PeLEDs the limited electroluminescence efficiency and spectral stability could be caused by multiple factors such as deep VBM and sub-bandgap states, [170,171] phase instability, and inhomogeneous distribution of mixed halides even in the precursor mixtures. [169] Nevertheless, the electrically driven ion migration could promote the phase segregation and defect formation processes in the perovskite emission layer and thus accelerate the deterioration of the PeLEDs.…”

Toward Stable and Efficient Perovskite Light‐Emitting Diodes

“…The development of PeLEDs with blue emission is key to the progress of full-color displays and white-light illumination. [16,19] Bromide-chloride mixing [25,[114][115][116][117] and size/dimensionality control [16,51,[118][119][120][121][122] are the most widely explored ways for tuning the emission color of PeLEDs and for achieving blue EL. As shown in Table 2, however, the performance of blue PeLEDs is far inferior to those of their near-infrared, red, and green counterparts (Table 1), [50,51,[53][54][55]90,91] which strongly limits the scope for practical applications.…”

Common Defects Accelerate Charge Carrier Recombination in CsSnI3 without Creating Mid-Gap States

“…3 Extensive studies have been performed to investigate MHPs, which show many favorable and unique properties, such as long electron and hole diffusion, 4,5 high charge carrier mobility, 6,7 high optical absorption, 8,9 and bandgap tunning over a wide energy range. 10,11 Due to the outstanding photoelectric properties and low cost to produce, 12 MHPs have attracted much attention for optoelectronic device applications, including solar cells, 1,2 light-emitting diodes, 13 photodetectors, 14 sensors, 15 etc. Although MHPs have excellent optoelectronic performance, several issues remain to be solved, such as stability upon exposure to humidity 16,17 and the toxicity of lead.…”

“…As one of the most rapidly growing photovoltaic devices, metal halide perovskite (MHP) solar cells convert solar energy to electricity and chemical fuels and are regarded as a promising technology due to ease of fabrication and high power conversion efficiency (PCE) that has reached 25.5% . Extensive studies have been performed to investigate MHPs, which show many favorable and unique properties, such as long electron and hole diffusion, , high charge carrier mobility, , high optical absorption, , and bandgap tunning over a wide energy range. , Due to the outstanding photoelectric properties and low cost to produce, MHPs have attracted much attention for optoelectronic device applications, including solar cells, , light-emitting diodes, photodetectors, sensors, etc. Although MHPs have excellent optoelectronic performance, several issues remain to be solved, such as stability upon exposure to humidity , and the toxicity of lead.…”