Research On High-Efficiency Exciplex Light-Emitting System Based On Novel Electron Acceptor Materials

Exciplex-based OLEDs(Organic light-emitting diodes)have been extensively studied in recent years.By choosing appropriate donor and acceptor materials,a series of TADF exciplexes have been constructed.Electron acceptors play an important role in exciplexes,and it is of great significance to develop new electron acceptors to construct high-efficiency exciplexes.However,there are still few studies on electron acceptor materials.To address this issue,four new electron acceptors were designed and synthesized.Their electrochemical and photophysical properties were studied.The specific research contents are as follows:(1)New electron acceptors,D3pyTRZ and D4pyTRZ,were designed and synthesized,and then combined them with different donors to construct novel exciplexes.All these devices exhibited excellent performances.The frontier orbital distributions of the receptors were analyzed through theoretical calculation.Photophysical properties of the blend films of the two molecules and a variety of donors as well as their pristine films were studied.Combining the two receptors with 13AB,13PXZB and mPTBC,three exciplexes OLEDs were fabricated.Among them,the device based on 13AB:D3pyTRZ exhibited a maximum external quantum efficiency of 13.0%,and the device based on D4pyTRZ:13PXZB demonstrated a maximum highest external quantum efficiency of8.72%.Hydrogen bonds and large steric hindrance enhance the rigidity of the exciplexes,and suppress the nonradiative transition.Therefore,the device based on D4pyTRZ:mPTBC has better performance,achieving an external quantum efficiency of17.2%at 560 nm,indicating that the development of new electronic acceptors based on Exciplex OLED devices of bulk materials are of great significance.(2)Two highly soluble electron acceptors,PyTRZ-tCz and PyTRZ-DtCz,were designed and synthesized,and their electrochemical and photophysical properties were studied.The rational design makes the PyTRZ-DtCz electron cloud overlap less,and the?E_ST is estimated to be 0.04 e V,which makes the triplet exciton upconversion process faster and the exciton utilization rate higher.The solubility of the molecule is improved by introducing a tert-butylcarbazole group into the molecule.Combining the two receptors with 13AB,TAPC,and DPh-PXZ,three exciplexes OLEDs were fabricated ranging from blue-green to orange-red.Among them,the orange-red OLED device based on PyTRZ-DtCz:DPh-PXZ has an external quantum efficiency of 6.53%,and the lighting voltage is 2.8 V at 580 nm.This work has certain reference significance for the exploration of solution-based OLED devices based on novel exciplex light-emitting systems.