激子态和电荷转移态的竞争对有机磁电导正负效应的调控  

Tuning the magnetoconductance from positive to negative upon the formation competition between exciton and charge-transfer states

作　　者：袁德[1] 陈秋松[1] 陈历相[1] 邹越[1] 陈平[1] 张巧明[1] 贾伟尧[1] 熊祖洪[1] 

机构地区：[1]西南大学物理科学与技术学院,重庆400715

出　　处：《中国科学：物理学、力学、天文学》2016年第3期65-73,共9页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(批准号:11374242;11404266);重庆市科委自然科学基金(编号:CSTC2010BA6002);中央高校基本科研业务费专项资金(编号:XDJK2014C081;XDJK2015C046)资助项目

摘　　要：利用具有激子态和电荷转移态(Charge-Transfer States,CTS)共存特性的PFOPV材料,本文制备了结构为ITO/PEDOT:PSS/PFOPV/Cs F/Al的聚合物发光器件,并测量了器件在不同偏压和温度下电流的磁场效应(又称磁电导效应(Magnetoconductance,MC))和电致发光光谱.实验发现,通过改变器件中激子态和CTS的相对比例,可以达到对MC低场(<40 m T)和高场(>40 m T)正负效应的有效调控.即当器件中CTS的相对比例较高时,MC的低场和高场均表现出明显的负磁电导效应,反之,则表现出正磁电导效应.采用经验公式对实验曲线进行定量分析表明,MC低场的正负效应可用系间窜越和反系间窜越过程来进行解释,而MC高场的正负转变则可归结为不同三重态与电荷相互作用的结果.本研究工作证明了三重态-电荷的反应方式对三重态中电子-空穴的间隔距离有强烈的依赖关系,同时为有机磁电导效应的有效调控提供了一条新的重要途径.By utilizing the PFOPV material with the characteristic of exciton states and Charge-Transfer States（CTS） coexisting, polymer light-emitting device with structure of ITO/PEDOT：PSS/PFOPV/Cs F/Al was fabricated, and the magnetic field effects on current（magnetoconductance, MC） were measured at different temperatures and bias voltages. We found that positive-negative inversion of MC could be tuned via modifying the ratio of exciton states to CTS, i.e., when the relative proportion of CTS was quite high in the device, the MC at both high fields（40 mT） and low fields（￡40 mT） showed significant negative effect. What＇s more, the MC displayed a positive effect in the opposite case. The quantitative analyses on MC effect through empirical formula, reveal that the inversion of MC from positive to negative at low fields is confirmed to be resulted from the intersystem crossing and reverse intersystem crossing processes. However, the transition at high magnetic fields can be attributed to the different reaction channels of triplets and charges. Our results demonstrate that the reaction paths of triplet-charge interactions are strongly dependent on electron-hole separation distance in triplets, moreover, enable a novel method to engineer the MC effect in organic semiconductors.

关 键 词：磁电导 聚合物发光器件 三重态-电荷反应 电荷转移态 

分 类 号：O482.5[理学—固体物理]