Abstract
Quantum dots (QDs) are expected to be applied to emitting materials used in wide-color-gamut displays. However, the development of low-toxic alternatives is necessary because QDs that exhibit high color purity and highly efficient emission contain toxic materials such as Cd. In the present study, quantum dot light-emitting diodes (QD-LEDs) prepared using ZnInP/ZnSe/ZnS QDs as InP-based QDs were fabricated, and their electroluminescence (EL) properties were investigated. The synthesized QD dispersion showed a green photoluminescence (PL) spectrum with a peak wavelength of 509 nm, a full-width at half-maximum (FWHM) of 41 nm, and a PL quantum yield of 59.8%. Tris[2,4,6-trimethyl-3-(pyridin-3-yl)phenyl]borane (3TPYMB), which is an electron-transporting material (ETM), was added to the emitting layer (EML) of the QD-LEDs. The QDs and the ETM were nonuniformly deposited, the density of QDs in the EML was reduced, and the process of injecting electrons and holes into the QDs was changed. 3TPYMB assisted in recombination in the QDs because the electron injection barrier from 3TPYMB to the QDs was sufficiently small and because the deep highest occupied molecular orbital level effectively blocked holes. As a result, the external quantum efficiency was improved from 0.24% to 1.01%, and stable EL spectra with a peak wavelength of 522 nm and an FWHM of 46 nm, similar to the PL spectrum of the QD film, were obtained without being dependent on luminance. A bright and stable green EL emission was achieved with an InP-based QD-LED blended with 3TPYMB.
Highlights
Ultra-high-definition television systems have been researched and developed to realize television services that provide realistic visual sensations so that the audience feels as though they are present at the scene.1 The video format [International Telecommunication Union Radiocommunication sector (ITU-R) recommendation BT.2020] defines the number of pixels and a wide-color-gamut color system, and the color gamut can express a wider range of colors than a conventional high-definition television
We thereby confirmed that quantum dots (QDs)-light-emitting diodes (LEDs) derived from the QDs without peripheral materials could exhibit appropriate EL spectra
The emitting layer (EML) of the fabricated quantum dot light-emitting diodes (QD-LEDs) was added with 3TPYMB, which has a sufficiently small electron-injection barrier into the QDs as an electron-transporting material (ETM) and a deep highest occupied molecular orbital (HOMO) level that blocks holes
Summary
Ultra-high-definition television systems have been researched and developed to realize television services that provide realistic visual sensations so that the audience feels as though they are present at the scene. The video format [International Telecommunication Union Radiocommunication sector (ITU-R) recommendation BT.2020] defines the number of pixels and a wide-color-gamut color system, and the color gamut can express a wider range of colors than a conventional high-definition television. The wide color gamut, which exceeds the color range of current flat-panel displays such as liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays, requires red, green, and blue primary colors with extremely high color purity.. As a light-emitting element for realizing a wide-color-gamut display, quantum dots (QDs) that emit light with high color purity scitation.org/journal/adv have attracted attention. QDs have semiconductor particles with sizes on the order of several nanometers as a core that emits light. As an example of their application in a wide-color-gamut display, QDs have been used as a backlight for LCDs. The white light for the backlight is generated by combining the PL of red and green QDs with the output of blue light-emitting diodes (LEDs).
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