Effect of Triplet State on the Lifetime of Charge Separation in Ambipolar D-A1-A2 Organic Semiconductors

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• 作者：Tianyang Wang ; Krishanthi C. Weerasinghe ; Haiya Sun ; Xiaoxia Hu ; Ting Lu ; Dongzhi Liu ; Wenping Hu ; Wei Li ; Xueqin Zhou ; Lichang Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 2, 2016
• 年：2016
• 卷：120
• 期：21
• 页码：11338-11349
• 全文大小：632K
• 年卷期：0
• ISSN：1932-7455

文摘

An ambipolar organic semiconductor with styrene based triphenylamine derivative (MTPA) as an electron donor (D), triazine group (TRC) as an electron acceptor (A₁), and 9,10-anthraquinone (AEAQ) as a second electron acceptor (A₂) has shown an 8-fold increase in the lifetime of charge separation with a high performance as solar cell materials with respect to the D-A₁ architecture and demonstrated a general D-A₁-A₂ architecture as a promising materials design strategy for photovoltaics. Here we synthesized and characterized two new D-A₁-A₂ compounds with perylene bisimide derivatives (PDI and PBI) as A₂ using an integrated experimental and computational method to study and compare the kinetics of three MTPA-TRC-A₂ systems. A two-step sequential decay pathway was observed in both MTPA-TRC-PDI and MTPA-TRC-PBI but a direct decay pathway in MTPA-TRC-AEAQ. The charge separated state with a lifetime of 22 ns in the PDI system and 75 ns in the PBI system relaxes to the corresponding triplet state followed by the decay to ground state in 827 ns and 29.2 μs, respectively. Thus, a triplet state with a lower energy than the charge separated state shortens the lifetime of the charge separated state but increases the overall lifetime of excited states.