Nanosecond response perovskite quantum dot light-emitting diodes with ultra-high resolution for active display application

Abstract

Perovskite quantum dots light-emitting diodes (PeLEDs) have been developed for next-generation high resolution display applications. However, the hindered charge injection and massive charge trapping due to the insulating and defective surface of quantum dots (QDs) usually lead to a slow rise in electroluminescence (EL) response, which makes it challenging to realize ultra-high refresh rate displays with nanosecond response. Herein, an ionic liquid 1-Butyl-3-methylimidazolium Trifluoromethanesulfonate ([BMIM]OTF) was used to enhance the crystallinity and reduce the surface area ratio of QDs, which effectively decreases defect state and injection barrier at the interface. Therefore, the rise time of EL response with steady-state is successfully reduced by over 75%. We further reduce the capacitance effect by decreasing the light-emitting unit area. Thus, ultra-high resolution (9072 pixel per inch) PeLEDs with light-emitting pixel size of 1.3 μm were realized, achieving a brightness exceeding 170,000 cd/m² and an external quantum efficiency up to 15.79%. Moreover, it achieves nanosecond ultrafast response time under steady-state, which is the fastest response time of PeLEDs reported so far. Our work represents the most advanced performance of ultra-high-resolution PeLEDs, and provides in-depth insights into the mechanism of improving their response speed, showing significant potential in high refresh rate active display application.

Fig. 1. The influence of [BMIM]OTF on QDs.

a The crystallization regulation process of QDs. b The PL and absorption graph. c The TEM size distribution of QDs. d, e XRD and PLQY graph. f TRPL spectra of QDs

Fig. 2. Defect passivation of QDs by [BMIM]OTF.

a–c DFT calculation for binding energy and differential charge density image of QDs. d Comparison of binding energies between different ligands for QDs. e XPS spectra of Pb-4f. f, g FTIR spectrum of C=N and -SO₃⁻ binding bond vibration. h, i Voltage–current density diagram of hole-only and electron-only devices. j Calculated trap density of control and [BMIM]OTF-3 devices. k TREL falling edge of devices

Fig. 3. The dynamics of carrier transport and injection in devices.

a The diagram of energy level structure. b UPS of QDs films. c KPFM images of Control and [BMIM]OTF-3 QDs film. d Schematic diagram of charge transfer and injection between QDs and the transport layers. e The impedance spectrum of the devices. f The capacitance-voltage curve of the devices. g TREL spectra of control and [BMIM]OTF devices. h–i TREL spectra with different voltages and frequency

Fig. 4. Performance of PeLEDs devices.

a Diagram of the device structure. b SEM image of device cross-section. c Stable EL spectra at different voltages. d–h J-V-L characteristics, EQE, Current efficiency, EQE distribution, and lifetime of the devices. i Lifetime and brightness comparison scatter plot of green perovskite quantum dots light-emitting diodes

Fig. 5. The application in high-resolution PeLEDs.

a Photoluminescence image of high-resolution QDs film. b J-V-L and c EQE of high-resolution devices, inset shows the distribution of EQE. d TREL plots of devices with different light-emitting unit areas. e Diagram of the relationship between response time and light-emitting unit area. f TREL plot of high-resolution device with a light-emitting area of 1 mm². g Comparison of the reported PeLEDs on the basis of steady-state EL response time and EQE. h Photograph of large area device (2.25 cm²)

Fig. 6. The application in AM-PeLEDs.

a AM-PeLEDs display structure diagram. b PL spectroscopy and microscopic photos of AM-PeLEDs. c The LOGO of Fuzhou University. d Multiple images displayed, including letters “FZU” and Chinese names for perovskite, as well as letters “LED”