Efficient Blue Light Emitting Diodes Based On Europium Halide Perovskites

Abstract

Flat panel displays enjoy 100 billion‐dollar markets with significant penetration in daily life, which require efficient, color‐saturated blue, green, and red light‐emitting diodes (LEDs). The recently emerged halide perovskites have demonstrated low‐cost and outstanding performance for potential LED applications. However, the performance of blue perovskite LEDs (PeLEDs) lags far behind red and green cousins, particularly for color coordinates approaching (0.131, 0.046) that fulfill the Rec. 2020 specification for blue emitters. Here, a high‐efficiency, lead‐free perovskite, CsEuBr3, is reported that exhibits bright blue exciton emission centered at 448 nm with a color coordinates of (0.15, 0.04), contributed from Eu‐5d→Eu‐4f/Br‐4p transition with an optical band gap of 2.85 eV. Further optical characterizations reveal its short excited‐state lifetime of 151 ns, excellent exciton diffusion diffusivity of 0.0227 cm2 s−1, and high quantum yield of ≈69%. Inspired by these findings, deep‐blue PeLEDs based on all‐vacuum processing methods, which have been demonstrated as the most successful approach for the organic LED industry, are constructed. The devices show a maximum external quantum efficiency of 6.5% with an operating half‐lifetime of 50 mins at an initial brightness of 15.9 cd m−2. It is anticipated that this work will inspire further research on lanthanide‐based perovskites for next‐generation LED applications.

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

“…Most recently, stable inorganic lead-free perovskites (e.g., CsEuBr 3 , Cs 3 Cu 2 X 5 , and Cs 3 Sb 2 X 9 ) have been designed for the fabrication of durable blue PeLEDs. [267][268][269][270][271] In particular, bivalent lanthanide ions have similar ionic radius to that of Pb 2+ and possess superior luminescence properties. The emission of lanthanide and actinide compounds can range from deep blue to infrared; thus, a series of novel perovskites remain to be developed for use in stable PeLEDs.…”

White-light defect emission and enhanced photoluminescence efficiency in a 0D indium-based metal halide

“…1–3 Their exceptional electronic and optical properties also encourage researchers to explore potential applications beyond solar cells. 4–8 In particular, low-dimensional organic–inorganic metal halides have been considered as efficient emitters due to the merits of structural and compositional tunability, extraordinary optical properties and facile synthesis by wet and solid-state methods, 9–17 which are potentially used in display technologies, solid-state lighting, scintillators, remote thermography and anti-counterfeiting labeling. 18–25 Notwithstanding the rapid advance in materials’ diversity and photoluminescence (PL) efficiency, their fundamental photophysical mechanisms are still elusive, which needs to be clarified not only from a basic science point of view, but for the purpose of designing novel materials with exceptional PL properties for practical applications.…”

Toward Stable and Efficient Perovskite Light‐Emitting Diodes

“…However, it has been observed that, as the central wavelength of EL approaches these wavelengths, the peak EQEs and operational lifetimes drop considerably. [25,118,[123][124][125][126][127][128] Figure 1. Schematic of general PeLED device structures, and energy levels of some commonly used HTL, ETL, and emissive perovskite materials.…”

“…However, it has been observed that, as the central wavelength of EL approaches these wavelengths, the peak EQEs and operational lifetimes drop considerably. [ 25,118,123–128 ]…”