Molecularly Doped Organic Afterglow Materials:Design,Preparation And Performance Study

Organic afterglow materials have good application prospects in the fields of bioimaging,organic light-emitting diodes,detection,information storage and anti-counterfeiting,due to their ultralong lifetime of excited states and easily adjustable optical properties.With the widespread attention in recent years,many strategies have been proposed for the design and preparation of organic afterglow materials.Nevertheless,there are still many deficiencies in optical performance.Because the interaction between different molecules can have a significant impact on the optical properties of organic afterglow materials,this thesis uses molecular doping as the main experimental method to prepare a series of molecularly doped organic afterglow materials,and in-depth research and exploration on the lifetime,quantum yield,luminescence color and duration of organic afterglow materials were carried out.High-efficiency and long-lifetime organic blue afterglow materials,sensitized organic afterglow materials and exciplex-based organic afterglow materials with ultralong emission duration have been achieved,and the application of organic afterglow materials has also been expanded.The specific research contents are as follows:(1)Since the strong hydrogen bonding between molecules can effectively suppress the non-radiative transition process,small organic molecules with multiple carboxyl groups and high triplet energy levels were selected as the guests,and the organic molecule with multiple hydrogen bond donor and acceptor sites was selected as the host.Through the construction of a complex hydrogen bonding by water molecules,a series of high-efficiency and long-lifetime organic blue afterglow materials were obtained.The best performing molecular doping system had ultralong lifetime and ultrahigh quantum yield(up to 1.67 s and 46.1%),with the CIE coordinates around(0.16,0.06).Moreover,through further research,it was found that there was an energy transfer process from the host to the guest.The way of sensitization is beneficial to increase the luminous intensity of molecularly doped organic afterglow materials.Based on the excellent performance of the organic blue afterglow materials,it was applied to rewritable lifetime-encrypted paper that can be printed with water inkjet,and the retention time of anti-counterfeiting patterns is even more than 1 month.The method is simple,environmentally friendly,cheap,and has a good encryption effect,highlighting the practical value and commercial value of organic afterglow materials.(2)Based on the work in the previous chapter,the dual-host approach greatly improved the stability of the organic blue afterglow materials.According to the energy storage characteristics of the organic afterglow,the organic blue afterglow material was used as the energy donor,and the organic light emitting material with matching energy level was selected as the energy acceptor.The sensitized organic afterglow material was realized by F(?)rster energy transfer from triplet excited state T1 of the donor to singlet excited state S1 of the acceptor,and the emission color change of the afterglow was modified.Moreover,since the energy donor exhibits a deep blue afterglow emission from 360 to 560 nm,it provides the possibility to fabricate more organic afterglow materials of other emission colors.(3)The long-lived charge separation state generated by light induction were used to design organic afterglow materials with ultralong emission duration by mixing strong donor molecule into different strong acceptor molecules.A series of exciplex-based organic afterglow materials with ultralong emission duration were obtained.And the emission duration of these materials was as short as several hundred seconds and as long as over 2 h,indicating that the acceptor molecules have a great influence on the photophysical properties of the exciplex-based organic afterglow materials.This is of great significance for the study of the selection of acceptor molecules in the exciplex-based organic afterglow materials.In summary,this thesis not only discusses the luminescence mechanism of molecularly doped organic afterglow materials,but also provides a viable path for further design and preparation of highperformance organic afterglow materials.