Design,Synthesis And Performance Investigations Of Exciplex-based Organic Afterglow Materials

Organic afterglow is a phenomenon showing continue emission after the cease of irradiation light.Due to unique optical phenomenon,organic afterglow materials have been widely used in the field of anti-counterfeiting,encryption,information storage,and optical bioimaging.In recent years,the developments and applications of new-type organic afterglow materials have received extensive attention from researchers.Exciplex-based organic long afterglow(RTP)materials with unique charge separation states have become one of the research focuses in the field of organic long afterglow due to their simple preparation process and long afterglow.However,on account of relatively short development time of exciplex-based RTP materials,there are still many problems to be solved.Currently,there are few reported exciplex-based RTP systems,and the selection mechanism of donor/acceptor materials is still unclear.These reported systems must be fabricated under a nitrogen atmosphere to prevent quenching of the CT states and CS states from oxygen and water.Phase separation in exciplex limits the development of the host-guest doping system.The thesis focuses on the design and synthesis of exciplex-based RTP materials with high environmental stability,and proposes molecular design strategies such as polymeric exciplexes and ionic bond interlocking.A series of space charge transfer complexes were prepared successfully,and the organic long afterglow properties have been analysed in scientific research.The specific work is as follows:(1)Aiming at the problem of few types of acceptor molecules in exciplex-based RTP materials,a new type of electron acceptor material was designed and synthesized based on the phosphine oxide functional group with strong electron-withdrawing ability.A series of novel exciplex-based RTP materials were successfully fabricated by melt-blending.The highly efficient exciplex RTP emission at room temperature from all the blended film,and the longest duration can reach 300 s.Through preliminary research,it is found that the reason may be that the CT state energy level of the formed exciplex is low,which avoids the energy returning to the host and the guest,and reduces the energy loss,thus realizing the ultra-long afterglow emission.The development of these new electron acceptors also provides ideas for the design and research of exciplex materials.(2)Aiming at the problems of poor air stability and phase separation of the organic longpersistence system of doped exciplexes,a class of polymer excimers based on space charge transfer was successfully prepared by radical polymerization of electron donors/acceptors.Composite organic long afterglow material.This single-component polymer-based exciplex not only has good structural stability,but also successfully solves the inevitable phase separation problem in the blend system,and also realizes stable stability in the air atmosphere.Even after being placed in the air for 100 h,it can still emit bright long-lived luminescence after excitation.Due to the poor rigidity of the polymer chain and the strong non-radiative transition of the system,the system has a relatively short duration,but it still provides an important reference for the design and development of high-stability exciplex RTP material.(3)In order to solve the problem of the short duration of the polymer-based exciplex RTP material system,a molecular design strategy of ionic bond interlocking was proposed in this chapter,and the material performance was successfully improved by ionizing triphenylphosphine polymer.The introduction of ionic bonds in the system can not only provide a rigid structure to suppress nonradiative transitions,but also stabilize the charge-separated state to achieve ultra-long organic longpersistence luminescence with a duration of 15 s.It provides a new research idea for the improvement of the performance of exciplex RTP material.