Blue Thermally Activated Delayed Fluorescence Organic Electroluminescent Devices with Carriers Regulating Structure by Employing the Gadolinium(III) Complex as a Hole Trapper

Abstract

In this work, a series of high-performance organic light-emitting devices based on blue thermally activated delayed fluorescence material DBA-DI were designed and fabricated by utilizing the gadolinium(III) complex as a hole trapper. After optimizing the doping concentration of the blue emitter, the Gd complex was codoped into the emitting layer (EML). Due to the high-lying highest occupied molecular orbital level (HOMO) of the Gd complex, superfluous holes within EML were effectively captured, thus improving carrier balance and broadening the recombination zone. Experimental results demonstrated that the codoped devices obtained significantly elevated electroluminescent (EL) performance by regulating carrier distribution and suppressing exciton quenching. Compared with nonco-doped devices, codoped devices displayed higher external quantum efficiency (EQE) and brightness with increased ratios of nearly 20% and over 30%, respectively. Eventually, the optimal codoped double-EML device obtained the maximum EQE, brightness, current efficiency, and power efficiency as high as 15.82%, 12,170 cd m^–2, 27.47 cd A^–1, and 31.96 lm W^–1, respectively. In addition, by further optimizing the thickness of the electron transport layer, a maximum EQE as high as 17.49% was realized.