Construction Of Afterglow Materials With Host-guest Structure And The Application In OLED Devices

Organic afterglow materials have been widely used in the fields of anti-counterfeiting and data encryption,bioimaging,and afterglow display due to their low cost,easy design and synthesis,high triplet state exciton utilization,and tunable photoelectric properties.Organic afterglow materials usually need to be in the crystalline state or under the protection of an insulating rigid substrate to exhibit afterglow properties,resulting in poor electrical properties which cause great challenges for their application in the field of electrogenic afterglow.Benefiting from the advantages of simple preparation process,low cost and many alternative material systems,this thesis adopts the host-guest doping strategy to construct a series of afterglow material with excellent electrically conductive properties and explores their applications in the field of Organic light-emitting devices.The specific work is as follows:（1）In this chapter,based on the host-guest doping structure,PPT and NPB with excellent charge transport properties are used as the host-guest molecules,where the host PPT can suppress the non-radiative transition of the triplet state exciton of the guest,thus enabling NPB with excellent phosphorescence properties to exhibit afterglow properties.The luminescence wavelength of NPB/PPT-doped films is around 438 nm and the lifetime reaches up to 414 ms.The OLED devices with NPB/PPT as the emitting layer material exhibit blue fluorescence emission（440 nm）and green afterglow emission（540 nm）before and after the applied voltage,respectively,where the green afterglow is up to 356 ms,and the maximum current efficiency（CE）and power efficiency（PE）of the devices are 1.01 cd A^-1 and 0.55 lm W^-1,respectively.This work in this chapter provides a new idea for the selection of host-guest afterglow material systems with excellent conductive properties and the construction of afterglow OLED devices.（2）Based on the previous investigation,in order to improve the efficiency of afterglow devices,4Cz IPN,a TADF material with high photoluminescence quantum efficiency（PLQY）,is chosen as the guest in this chapter.4Cz IPN/PPT-doped films with a luminescence wavelength is around 500 nm and have a lifetime of up to 283 ms,showing excellent afterglow luminescence performance.The afterglow lifetime of the OLED device with 4Cz IPN/PPT as the emitting layer material reaches 268ms,and the maximum CE and PE of the device are 35.05 cd A^-1 and 17.89 lm W^-1,respectively.The work in this chapter demonstrates that the TADF material can be used to build high performance host-guest afterglow material and high efficiency afterglow OLED device,which provides a reference for the preparation of high efficiency afterglow OLED device.（3）Phosphine-based materials have the advantages of high carrier mobility and high triplet state energy level,which can be used as host materials to ensure effective energy transfer,and also play an important role in improving the concentration quenching and device efficiency roll-off.In this chapter,DBTSPO and NPB are selected as the host and guest molecules,in which the luminescence wavelength of NPB/DBTSPO doped film is around 430 nm and the lifetime is up to 397 ms.The green afterglow of OLED devices with NPB/DBTSPO as the luminescence layer material is up to342 ms,and the maximum CE and PE of the devices are 0.41 cd A^-1 and 0.15 lm W^-1,respectively.The work in this chapter shows that phosphine-based materials can be used as the host material to build afterglow material systems and afterglow OLED devices,which provide the possibility to build more afterglow OLED devices.