侧链基团对聚合物薄膜瞬态发光性能的影响

采用飞秒激光光谱技术比较研究了两种卟啉侧链聚合物:卟啉丙烯酸酯-苯乙烯共聚物P[(por)A-S]和卟啉铁(Ⅲ)丙烯酸酯-苯乙烯共聚物P[(por)FeA-S]的瞬态发光性能。并采用纳秒激光光谱技术测量了小分子卟啉(TPP)的荧光动力学过程。结果表明:P[(por)FeA-S]具有比P[(por)A-S]快得多的荧光弛豫过程,而P[(por)A-S]的荧光寿命远小于小分子卟啉的荧光寿命。对上述过程进行了分析,P[(por)A-S]的荧光衰变主要来源于聚合物分子链间的相互作用;而P[(por)FeA-S]的荧光衰变除了来源于聚合物分子链间的相互作用外,中央金属离子与配位体之间的电荷转移也对卟啉发色基团的激发态超快无辐射弛豫具有重要的影响,对上述过程的产生机理进行了讨论。

The Influence of the Side-chain Groups on Luminescence of Porphyrin Side-chain Polymers

Luminescent conjugated polymers have been extensively studied due to their use as active materials in cheap and efficient light-emitting diodes(LED).However,despite the fact that many exciting progresses have been achieved,a lot of work is still needed to develop new polymers(or modified version of existing ones) that can emit red,green and blue light.Doping of the emission layers in LEDs with luminescent dyes can control the colour of emission as well as improve device efficiency.Porphyrins have potential applications in LED because of their pure red-light emission and optimized efficiency over all other fluorescent materials.However,there have been few reports about them used in LEDs.This is due to their propensity to π-π stack,which causes the material non-luminescent in the solid state.These problems can be overcome by incorporating porphyrin chromophores as the side-chain groups to control the porphyrin-porphyrin interactions in solid states.In this paper,the transient fluorescence dynamics of two porphyrin side-chain polyers,P[(por)A-S] and P[(por)FeA-S],were measured by using femtosecond time-resolved luminescence spectroscopy.Using nanosecond spectroscopic technology,we also measured the transient fluorescence dynamics of the monomer porphyrin molecules(TPP).The results show that all the transient luminescence decays are composed of two components:an initial fast decay(58 ps for P[(por)FeA-S],and 200 ps for P[(por)A-S]),and a following slowing relaxation processes(217 ps for P[(por)FeA-S],and 2.1 ns for P[(por)A-S]).The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the porphyrin side-chain polymer films.The intermolecular interactions result in the faster fluorescence decay than that of TPP.The intramolecular charge transfer and the intermolecular interactions result in the ultrafast fluorescence decay in P[(por)FeA-S] compared with that of P[(por)A-S].