Suppressing High-Order Phase for Efficient Pure Red Quasi-2D Perovskite Light-Emitting Diodes

Abstract

Quasi-two-dimensional (quasi-2D) perovskites are promising for the realization of spectrally stable pure red perovskite light-emitting diodes (PeLEDs) with a single iodide component, because they avoid the halide separation that red three-dimensional perovskites of mixed halides have faced. However, the distribution of high-order phases in solution-processed quasi-2D perovskite films causes the spectral shift away from the pure red region. Here, we introduced a simple approach of adding excessive ligand combinations to redistribute the phase distribution of quasi-2D perovskite and to inhibit the high-order phase. Appropriate excess organic ligands will not affect charge injection but will keep the efficient energy funneling and passivate the defect. The narrowed phase distribution reduced the band tail state and restrained reverse charge transfer, resulting in enhanced radiation recombination. We obtained efficient and spectrally stable pure red PeLEDs at 638 nm (approaching the Rec. 2020 specification) with a peak EQE of 11.8% and maximum luminance of 1688 cd/cm2. This study provides guidance for future developments of highly efficient pure red PeLEDs.

In Situ Halide Insertion for Efficient and Stable Pure‐Red Perovskite Light‐Emitting Diodes

“…[34] Although stable red emission peaks were achieved by modulation of BA concentrations, the constructed PeLEDs only showed a poor EQE of 0.41% at 638 nm and broad full width at half-maximum (fwhm) of 61 nm due to the unexpected wide perovskite phase distribution. Besides the sole spacer cation, the dual spacer cations, such as phenylbutylammonium (PBA) and 𝛼-methylbenzylammonium (MBZA), [35] phenethylammonium (PEA) and 1-naphthylmethylammonium (NMA), [36,37] and ethylamine (EA) and NMA [38] were also adopted to tune the phase distribution for red emission by carefully optimizing the co-spacer ratios. Typically, plenty of organic ammonium cations are added into the quasi-2D perovskite precursor to reduce the layers of the Pb-I octahedron for red emission.…”

Blue-emitting perovskite nanocrystals with enhanced optical properties through using NaBH4

“…(FA + ), X = Cl -, Br -, I -) have attracted attention as optical materials for light-emitting diodes (LEDs), lasers and other devices owing to their narrow full width at half maximum and color tunability over the entire visible range. [1][2][3][4][5][6][7][8][9][10][11][12][13] Thus, improving the optical properties of red, green and blue (RGB)-emitting PeNCs is important. [14][15][16] Bromideand iodide-based PeNCs (APbBr 3 , APbI 3 ) with a high photoluminescence quantum yield (PLQY) of over 90% have been reported for green-and red-emitting materials.…”

High-Performance Pure Red Quasi-Two-Dimensional Perovskite Light-Emitting Diodes with Bifunctional Potassium Trifluoroacetate Additive

“…3,21 Although these studies have made progress for pure red quasi-2D PeLEDs, their EQEs still fall behind pure red PeLEDs based on mixed bromide-iodide perovskites or QDs perovskites. 22 Quasi-2D perovskites possess mixed phases with different nvalues (n represents the thickness of inorganic octahedral [PbI 6 ] 4− layers), and cascade energy funneling occurs from low-n phase to high-n phase (emission phase). 23−25 Efficient energy transfer requires the rapid transfer of carriers to the emission phase to avoid the trapping process.…”

“…Pure iodide-based quasi-2D PeLEDs take advantage of spectral stability, and their emission peak wavelength can be tuned by regulating component ratio or substituting the organic spacer cations. , In 2018, Ma et al controlled the molar ratio of organic salts to tune the emission color of quasi-2D PeLEDs from red to deep red and obtained a spectrally stable pure red PeLED with a peak external quantum efficiency (EQE) of 0.41% at 638 nm . Around the same time in 2021, our group and Gao’s group achieved pure red PeLED with a peak EQE of 12.41% at 635 nm and 10.8% at 640 nm, respectively, by simply adjusting the ratio of dual spacer cations. , Although these studies have made progress for pure red quasi-2D PeLEDs, their EQEs still fall behind pure red PeLEDs based on mixed bromide-iodide perovskites or QDs perovskites …”