二异丙基苯基和十一烷取代的聚乙烯二酰亚胺薄膜激发态动力学研究

Insight of Excited State Dynamics in Perylenedimide Films with Diisopropylphenyl-and Undecane-Substitution

苝二亚胺及其衍生物的堆积模式与其分子结构相密切关,进而影响其激发态动力学.通过调节单体、二聚体、J聚体或H聚体等苝二亚胺分子的堆叠模式,可以有效调控其激发态动力学.本文合成了两种苝二亚胺衍生物,十一烷取代的苝二亚胺和二异丙基苯基取代的苝二亚胺,并用旋涂法制备薄膜.利用时间分辨荧光谱和瞬态吸收光谱,系统地研究了两种苝二亚胺非晶膜的激发态动力学.实验结果表明,由于分子存在强耦合作用,这两种薄膜在光激发后都形成了激基缔合物.有趣的是,二异丙基苯基取代的苝二亚胺中瞬态吸收光谱表现了明显的三线态瞬态吸收信号,由此推断二异丙基苯基取代的苝二亚胺薄膜在光激发后产生单线态裂分.该研究阐明非晶态苝二亚胺薄膜中激发态动力学,并为更好地理解和调控非晶态膜的激发态特性提供了借鉴.

The aggregation of perylene diimide(PDI)and its derivatives strongly depends on the molecular structure and therefore has a great impact on the excited states.By regulating the molecular stacking such as monomer,dimer,J-and/or H-aggregate,the formation of different excited states is adjustable and controllable.In this study,we have synthesized two kinds of PDI derivatives:undecane-substituted PDI(PDI-1)and diisopropylphenyl-substituted PDI(PDI-2),and the films are fabricated with spin-coating method.By employing photoluminescence,time-resolved photoluminescence,and transient absorption spectroscopy,the excited-state dynamics of two PDI amorphous films have been investigated systematically.The result reveals that both films form excimers after photoexcitation mainly due to the stronger electronic coupling among molecule aggregate in the amorphous film.It should be noted that the excited state dynamics in PDI-2 shows a singlet fission like process,which is evidenced by the appearance of triplet state absorption.This study provides the dynamics of excited state in amorphous PDI films,and paves the way for better understanding and adjusting the excited state of amorphous PDI films.