Electronic Structural Insight into High‐Performance Quantum Dot Light‐Emitting Diodes

Abstract

Quantum dot light-emitting diodes (QD-LEDs) are highly promising light sources with excellent figures of merit. Although great successes have been achieved in elevating some key parameters to an ideal level, QD-LEDs with superior performance in all aspects have rarely been realized. Herein, by exploring crystalline structure-dependent electronic properties, it is shown that QD-LEDs can simultaneously exhibit high external quantum efficiency, roll-off-free under high brightness, and dramatically improved operational stability. This improved performance stems from the crystal phase engineering of QD. Reduced structure symmetry in the wurtzite phase introduces an unneglectable internal crystal field compared with the zinc-blende one, which raises both the conduction and valence band energy levels, thus, facilitating a more balanced charge injection. The crystal phase-optimized superior-comprehensive performance in the QD-LED offers a novel degree of freedom for device engineering and promotes commercial applications for the upcoming display and illumination technologies.

Carboxylic‐Free Synthesis of InP Quantum Dots for Highly Efficient and Bright Electroluminescent Device

“…Due to the size-dependent emission color, narrow spectra, high luminescent efficiency, good stability, simple & scalable synthesis, and compatibility with solution process, colloidal quantum dots (QDs) are expected to be used in the nextgeneration commercialized display products. [1][2][3][4][5][6][7][8][9][10][11][12] Nowadays, the external quantum efficiencies (EQEs) and luminance of quantum dot light-emitting diodes (QLEDs) have reached was used in the synthesis of InP QDs. [30] On the other hand, another alternative, tris(dimethylamino)phosphine (DMA) 3 P, which possesses moderate reactivity as well as no pyrophoricity was more extensively used recently.…”

“…Due to the size‐dependent emission color, narrow spectra, high luminescent efficiency, good stability, simple & scalable synthesis, and compatibility with solution process, colloidal quantum dots (QDs) are expected to be used in the next‐generation commercialized display products. [ 1–12 ] Nowadays, the external quantum efficiencies (EQEs) and luminance of quantum dot light‐emitting diodes (QLEDs) have reached 30.9% and 3 300 000 cd m −2 , 28.7% and 1 680 000 cd m −2 , 21.9% and 62 600 cd m −2 for red, green, and blue, respectively. Their lifetimes are also long enough for some commercialization requirements.…”

Deep‐Red InP Core‐Multishell Quantum Dots for Highly Bright and Efficient Light‐Emitting Diodes

“…Colloidal quantum dots (QDs) are semiconductor nanostructures in which excitons are bounded in three dimensions. [1] They DOI: 10.1002/adom.202300612 have been widely used in light-emitting diodes (LEDs), [2][3][4][5][6] solar cells, [7,8] biomarkers, [9,10] lasers, and sensors [11] for their high photoluminescence quantum yield (PLQY), good monochromaticity, continuously adjustable emission wavelength, high stability, low preparation cost, and easy mass production. [12,13] Especially, quantumdot LED (QLED) is one of the most pursued technologies for next-generation display and lighting applications with both high energy efficiency and wide color gamut.…”

Changes in Hole and Electron Injection under Electrical Stress and the Rapid Electroluminescence Loss in Blue Quantum‐Dot Light‐Emitting Devices

“…Results show that the EL loss results primarily from a deterioration in charge balance caused by changes in hole and electron injection in the blue QDs that occur while the devices are under electrical bias, and is not associated with permanent changes in the QDs or their PLQY as is sometimes suspected. [14,34,35] The changes in charge injection are also found to be partially reversible upon stopping the electrical bias, and therefore using pulsed (instead of continuous) electrical driving can slow down some of these effects, resulting in a 2.5× longer device LT50, from the same initial luminance of 500 cd m −2 and at a similar average current density of 10 mA cm −2 . Capacitance-voltage (C-V) measurements on unaged and electrically-aged devices compared with current density-voltage-luminance (J-V-L) characteristics show that the threshold voltage decreases and the turnon voltage increases after aging due to the changes in charge injection efficiencies which are corroborating these conclusions.…”