中文摘要：

在基于电荷转移（charge transfer,CT）态的发光器件中,CT态的演化及其相互作用对器件发光有重要影响.将分子内CT态材料4-（Dicyanomethylene）-2-tert-butyl-6-（1,1,7,7-tetramethyljulolidin-4-yl-vinyl）-4H-pyran（DCJTB）以不同浓度掺杂于磷光主体材料1,3-bis（9-carbazolyl）benzene（m CP）中,通过测量器件电致发光的磁场效应（magnetoelectroluminescence,MEL）,来研究器件中CT态及其相互作用.在±500 m T的磁场范围内,MEL曲线展示出奇特的变化：当掺杂浓度从高浓度（20%）降至低浓度（5%）时,低场部分从正转变为负;而高场部分没有明显的浓度依赖关系,均表现为缓慢下降.另外,在不同温度下MEL高低场部分的幅度都有很大变化.这些变化表明,器件中存在CT态的系间窜越、反向系间窜越过程,以及CT态间的湮灭过程,且这些过程受到掺杂浓度和温度的影响,导致延迟发光的变化.

英文摘要：

Up to date, both reverse intersystem crossing（RISC） and triplet–triplet annihilation（TTA） are effective approaches to improve the internal efficiency of fluorescent OLEDs, because they can make the best of triplet excitons to generate delayed fluorescence. The energy difference between singlet and triplet excited states（△ES-T） of special intramolecular charge transfer（CT） species is quite small, which make it posible for the participation of the CT species in RISC and TTA. When the RISC and TTA coexist in fluorescent OLEDs, the utilization of triplet excitons should be much better. The goal of this work was to demonstrate the feasibility of the coexistence. However, determining whether the coexistence happens in fluorescent OLEDs is not an easy task, because the general methods can hardly distinct the delayed fluorescence is originated from which approaches. Fortunately, both RISC and TTA are highly spin-dependent processes that can generate sizable magneto-electroluminescence（MEL） responses in OLEDs. Typically, the MEL response of RISC is a low-field effect, i.e., the MEL decreases rapid within the low-field regime（〈5 mT） and then tends to saturation. Differently, the MEL of TTA exhibits a slight increase within the range of 20 mT but a remarkable decrease in the high-field regime（〉20 mT）. Hence, the MEL can be used as a novel tool to discern RISC and TTA in fluorescent OLEDs. Following such strategy, in this work, we firstly fabricated the devices by doping different concentrations of intramolecular CT states specie 4-（Dicyanomethylene）-2-tert-butyl-6-（1,1,7,7-tetramethyljulolidin-4-yl-vinyl）-4H-pyran（DCJTB） into phosphor host material 1,3-bis（9-carbazolyl）benzene（mC P） and then measured the MEL responses of these devices at room temperature. It exhibited that the sign of low-field（〈5 mT） component turned from positive to negative as the doping concentration decreasing from 20% to 5%, this was same to the situation for the high-field（B〉20 mT） b