Modulation of recombination zone position for quasi-two-dimensional blue perovskite light-emitting diodes with efficiency exceeding 5%

Abstract

In recent years, substantial progress has been made in developing perovskite light-emitting diodes with near-infrared, red and green emissions and over 20% external quantum efficiency. However, the development of perovskite light-emitting diodes with blue emission remains a great challenge, which retards further development of full-color displays and white-light illumination based on perovskite emissive materials. Here, firstly, through composition and dimensional engineering, we prepare quasi-two-dimensional perovskite thin films with improved blue emission, taking advantages of reduced trap density and enhanced photoluminescence quantum yield. Secondly, we find a vertically non-uniform distribution of perovskite crystals in the PEDOT:PSS/perovskite hybrid film. Through modulating the position of the recombination zone, we activate the majority of quasi-two-dimensional perovskite crystals, and thus demonstrate the most efficient blue perovskite light-emitting diode to date with emission peak at 480 nm, record luminance of 3780 cd m −2 and record external quantum efficiency of 5.7%.

Recent advances and prospects toward blue perovskite materials and light‐emitting diodes

“…A, The schematic diagram shows difference in carrier recombination. B, EQE of PeLEDs with different PEDOT:PSS thicknesses . Copyright 2019, Springer Nature.…”

“…Over the past few years, LEDs based on metal halide perovskites (MHPs) have shown great potential as candidate in blue-emissive LEDs. 12,[21][22][23][24][25][26][27][28][29] MHPs possess excellent optoelectronic properties, [30][31][32][33][34][35][36][37][38][39] such as narrow emission linewidths (full width at half-maximum [FWHM] < 20 nm), precise tunable bandgaps (ranging from ultraviolet to near-infrared), and high charge carrier mobility and defect tolerance. The ultrahigh color purity and wide color gamut (~150%; the color gamut level for the national television standards committee [NTSC] standard is <100%) grant MHP LEDs great prospects in display applications.…”

Light Generation in Lead Halide Perovskite Nanocrystals: LEDs, Color Converters, Lasers, and Other Applications

“…A clean bandgap structure enables LHP‐NCs to produce an energy‐efficient and narrow band emission, even in the absence of ligands for passivating surface defects . Any remaining shallow bandgap states caused by surface defects can be effectively passivated using ligands . The unique energy diagrams and the resulting high defect tolerance of LHP‐NCs result in superior optical and electrical characteristics even when LHP‐NCs are fabricated by a crude synthesis However, the low luminous efficiency of LHP‐NCs at low excitation densities suggests that there is still considerable loss from trap‐induced nonradiative recombination .…”

“…Light emission from lead halide perovskites (LHPs) was reported over a decade ago; however, weak emissions at room temperature hindered the application of LHPs in light‐emitting devices because LHPs did not show any electroluminescence at the time . In the past few years, LHPs have returned to the spotlight in the form of nanoscale emitters because of their superior features in light generation and resulting applications . Low‐cost solution processing techniques are used to fabricate LHP nanocrystals (LHP‐NCs), and impressive achievements have been made in using LHP‐NCs in high‐brightness light‐emitting diodes (LEDs) with high external quantum efficiency (EQE) and as color converters for lighting and full‐color displays that have a wide color gamut and near‐unity luminous efficiency .…”

“…The prompt emission of LHP‐NCs has resulted in their being selected as color converters for light indoor fidelity (Li‐Fi) in short‐distance wireless data transmission . As the most attractive application, red and green LEDs exhibit much higher performances with EQEs >20% and high brightness that are comparable to organic LEDs and CdSe quantum dot LEDs; however, blue LEDs still have an EQE of ≈5.7% and a maximum brightness of 3780 cd m −2 . LHP‐NCs have narrow band emissions and are therefore not the best color convertors for white LEDs in lighting; however, low‐cost phosphors exhibit similar performance to lanthanide based white LEDs .…”