Purely organic electroluminescent material realizing 100% conversion from electricity to light.

Hironori Kaji,Yasujiro Murata,Chihaya Adachi,Shosei Kubo,Katsuaki Suzuki,Hajime Suzuki,Atsushi Wakamiya,Katsuyuki Shizu,Takeshi Komino,Hajime Oiwa,Tatsuya Fukushima,Furitsu Suzuki

doi:10.1038/ncomms9476

Abstract

Efficient organic light-emitting diodes have been developed using emitters containing rare metals, such as platinum and iridium complexes. However, there is an urgent need to develop emitters composed of more abundant materials. Here we show a thermally activated delayed fluorescence material for organic light-emitting diodes, which realizes both approximately 100% photoluminescence quantum yield and approximately 100% up-conversion of the triplet to singlet excited state. The material contains electron-donating diphenylaminocarbazole and electron-accepting triphenyltriazine moieties. The typical trade-off between effective emission and triplet-to-singlet up-conversion is overcome by fine-tuning the highest occupied molecular orbital and lowest unoccupied molecular orbital distributions. The nearly zero singlet–triplet energy gap, smaller than the thermal energy at room temperature, results in an organic light-emitting diode with external quantum efficiency of 29.6%. An external quantum efficiency of 41.5% is obtained when using an out-coupling sheet. The external quantum efficiency is 30.7% even at a high luminance of 3,000 cd m−2.

Highlights

Efficient organic light-emitting diodes have been developed using emitters containing rare metals, such as platinum and iridium complexes
internal quantum efficiency (IQE) is obtained from IQE 1⁄4 b Â g Â FPL, where b is the exciton generation factor resulting in photons, g is the carrier balance ratio of holes and electrons, and FPL is the photoluminescence (PL) quantum yield (PLQY)
DACT-II was used as an emitting material for organic light-emitting diodes (OLEDs) (DACT-II devices)

Summary

Introduction

Efficient organic light-emitting diodes have been developed using emitters containing rare metals, such as platinum and iridium complexes. The DACT-II-1 device contains emission from TAPC and/or CBP (Supplementary Figure 6 shows the PL spectra of the respective materials).

Results

Conclusion