| Organic optoelectronic materials have been widely applied into organoelectronics including organic light emitting diodes(OLEDs), organic field effect transistors(OFETs), organic photovoltaic cells(OPVs), organic memories and lasers due to their excellent optoelectronics properties. The modulation of the optoelectronic properties of organic materials has been realized after the flourishes developments over the past decades. However, only certain optoelectronic properties can be effectively enhanced without negatively influencing on other properties due to the intrinsic correlations between the molecular structures and properties in most cases, leading to limited improvecment of the comprehensive performance; additionally, the emission lifetime of the organic materials is always at the order of ns-ms, owing to their highly active excited states, resulting in little success in realizing the purely organic materials with ultralong lifetime. Therefore, benefiting from the excellent properties of the aryl phosphine optoelectronic materials, this thesis not only establish a new design strategy for selective tuning the optoelectronic properties for organic materials through resonance variation, but also propose a new approach for realizing the afterglow emission in organic materials through introducing the heteroatom to promote the intersystem crossing and the special energy trap—“H-aggregation” to trap and stabilize the triplet excitons. The detail researches are as follows:1) Design, synthesis and investigation of the dynamically self-adaptive host materials with N-P=O resonance structure.Four host materials with N-P=O resoancne structure based on the carbazole and phosphine oxide derivatives were successfully designed and synthesized. The photophysical and electrochemical properties of the N-P=O resonance host were evaluated. Those results revealed that the resonance hosts can selectively enhance the electronical performance of the organic materials without influencing on the excellent photophycail properties in a dynamic process. The blue PHOLEDs with the N-P=O molecules as the hosts showed high performance with a low driving voltage of 2.4 V, external quantum efficiency(EQE) of 16.5%, current efficiency(CE) of 32.3 cd/A, power efficiency(PE) of 37.2 lm/W, which are among the best data of low voltage-driving blue PHOLEDs reported to date.2) The investigation of the PHOLEDs based on solution-processed N-P=O resonance host.Solution-processed PHOLEDs using N-P=O resonance molecule with excellent optoelectronics properties as host were fabricated. Benefiting from the balanced charge transport property offered by the dynamically adaptive characteristics in charge-transport processes of resonance host and broad recombination zone of the solution-processed PHOLEDs, the blue and white PHOLEDs obtained high efficiencies with low driving voltage of 3.6 and 3.9 V, EQE of ~16.5 and 14.7%, CE of 29.9 and 38.8 cd/A, PE of 19.9 and 18.8 lm/W, respectively. More importantly, the devices showed excellent stability at high luminance(1000 cd/m2) as revealed by small efficiency roll-off.3) Design, synthesis and investigation of the dynamically self-adaptive smart host materials with N-P=S resonance structure.Four host materials with N-P=S resoancne structure were successfully designed and synthesized. The optoelectronic properties of the N-P=S resonance host were investigaed through a combined experimental and theoretical study. Those results demonstrated that the electronical performance can be further regulated without nagetively influencing on the photophysical properties through modulating the resonance variation. The high efficiencies blue, white PHOLEDs and green and blue TADF OLEDs hosted by N-P=S resonance hosts were resulted with low driving voltages of 2.9, 3.6, 4.4 and 3.4 V, EQE of 21.7, 16.4, 12.2 and 11.9%, CE of 39.7, 40.6, 38.5 and 22.2 cd/A,PE of 36.6, 32.3, 27.3 and 15.8 lm/W, respectively.4) Design, synthesis and investigation of purely organic afterglow materials based on the aryl phosphine derivatives.Three purely organic afterglow materials based on the aryl phosphine derivatives at room temperature were successfully synthesized through rational molecular design. Those materials show ultralong lifetime of ~0.67 s and tunable emission color. The luminescence mechanisem of afterglow emission is composed of three processes: i) the singlet excitons transform to triplet states through intersystem crossing for forming triplet excitons, ii) the triplet excitons transform to H-aggregation and was trapped and stabilized by H-aggregation, iii) the trapped and stabilized triplet excitons slowly decay to the ground state accompanying with afterglow emission. The new emerged applications in the fields of organic anti-counterfeiting, storage encryption and data security were developed based on the purely organic afterglow materials. |
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