| In recent decades,metal-free organic luminogens with sundry luminescent properties are of intense interest due to their extensive potential applications for the development of fields such as optical storage,biological probes and imaging,sensors,lasers and organic light emitting diodes（OLEDs）.The organic light-emitting processes,including photoluminescence（PL）and electroluminescence（EL）have thus been well researched.Especially,the interactions between the excited states are fascinating,important and complex due to its decisive role in the flexible implementation of various luminescent properties,e.g.fluorescence,room temperature phosphorescence（RTP）,thermally activated delayed fluorescence（TADF）.At present,these kinds of materials have been widely developed,but there is still a prominent problem to be solved,e.g.for thermally activated delayed fluorescence,deep blue materials and solvent-processing materials are deficient and the color purity is poor;for room temperature phosphorescence,materials shortage,strict realization condition and restricted to the PL research process only.Thus to solve these problems,this paper puts forward a series of important strategies.In chapter 2,we designed and synthesized D-A alternating delayed fluorescence polymer materials for the first time.A C-N coupling polymerization method is adopted to guarantee the proper conjugate length and realize the deep blue emission.Thereinto,solution-processing OLED was fabricated with P3-SO2 as the emitter,exhibiting a high maximum external quantum efficiency（EQE）of 5.3%and a high power efficiency of 4.2 lm/W with Commission Internationale de l’Eclairage（CIE）coordinates of（0.16,0.10）,which is very close to the（0.14,0.08）standard defined by the National Television System Committee（NTSC）.In chapter 3,based on the results of chapter 2,we successfully constructed a series of polymer TADF materials using the energy transfer strategy,which also realized the effective spectral regulation.The solution-processing OLEDs were fabricated with P1-P4 as the emitters.The sky-blue-emitting device based on P1 achieved a maximum EQE of 6.1%with CIE coordinates of（0.20,0.28）and the higher maximum EQE reached 8.7%for bluish-green-emitting device based on P3.In chapter 4,interestingly,also based on the accidental discovery in chapter 2,we developed a series of soluble cyclic blue TADF small molecules.In the PL measurements of the spinning neat films and crystal powders,the room temperature phosphorescence property was discovered and further verified by careful photophysical characterization,crystal analysis and theoretical calculations.It is different from that RTP can only be realized under single crystal condition or under the host-guest system.In chapter 5,referring to the research achievements of cyclic molecules,we designed and synthesized a series of ultra-deep blue cage molecules with high solubility and very small full-width at half-maximum（FWHM）.By adjusting the push-pull electron capability of the units,the small the energy difference between the singlet and triplet excited states(ΔEST)can be realized,which leads to the effective TADF.Among them,3SO2 shows delay fluorescence characteristics.The device based on 3SO2 exhibitted unreported performance for TADF-OLEDs with maximum EQE of 2.63%,FWHM of 35 nm and CIEy value of less than 0.05.In chapter 6,through the construction of simple units（binaphthyl and amidogen）,we synthesized a cyclic compound with the dual luminescence properties of room temperature phosphorescence and circularly polarized luminescence（CPL）.Subsequently,we systematically explored the different implementation condition of room temperature phosphorescence and used theoretical calculation to explain the circularly polarized signal inversion phenomenon under different circumstances.At the same time,we further studied the electroluminescent process of this CPL-RTP material. |
