Enhancing the efficiency and the luminance of quantum dot light-emitting diodes by inserting a leaked electron harvesting layer with thermal-activated delayed fluorescence material

Abstract

Abstract In order to utilize the leaked electrons from emission layer (EML) and simultaneously enhance the performance of the quantum dot light-emitting diodes (QLEDs), a blue thermally activated delayed fluorescence (TADF) material, 10,10'-(4,4-Sulfonylbis(4,1-phenylene))bis(9,9-dimethyl-9,10-dihydroacridine) (DMAC-DPS), was inserted as an interlayer between hole transport layer (HTL) and quantum dot (QD) EML. In the TADF inserting layer, the leaked electrons from the EML can form excitons with the injected holes from the HTL, followed by energy transfer from the TADF material to the QD EML. The TADF inserting layer is also expected to promote the hole injection from HTL to EML and to alleviate the electron accumulation situation at QD/HTL interface. Therefore, compared with standard QLED without TADF inserting layer, the utilization of electrons in the QLEDs with TADF interlayer are enhanced and the charge carriers are more balance in QD EML. These benefits enable a 1.17-fold increment for current efficiency (from 8.9 cd/A to 10.44 cd/A) and 1.41-fold improvement for maximum luminance (from 44781 cd/m2 to 63458 cd/m2) in the optimal QLED employing 5 nm TADF interlayer.