Competition between Singlet Fission and Charge Separation in Solution-Processed Blend Films of 6,13-Bis(triisopropylsilylethynyl)pentacene with Sterically-Encumbered Perylene-3,4:9,10-bis(dicarboximide)s
Competition between Singlet Fission and Charge Separation in Solution-Processed Blend Films of 6,13-Bis(triisopropylsilylethynyl)pentacene with Sterically-Encumbered Perylene-3,4:9,10-bis(dicarboximide)s
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DOI：
10.1021/ja2080482
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发表时间：
2012-01-11
影响因子：
15
通讯作者：
Wasielewski, Michael R.
中科院分区：
文献类型：
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作者：
Ramanan, Charusheela;Smeigh, Amanda L.;Wasielewski, Michael R.
N,N-双(2,6-二异丙基苯基)苝-3,4:9,10-双(二甲酰亚胺)(1)和1,7-联苯(2)和1,7-双(3,5-二叔丁基苯基)(3)衍生物与6,13-双(三异丙基甲硅烷基乙炔基)并五苯共混的薄膜的光物理和形貌研究人员对（TIPS-Pn）作为有机光伏（OPV）器件中光活性层的潜在用途进行了研究。增加苝-3,4:9,10-双(二甲酰亚胺) (PDI) 的 1,7-取代基的空间体积可阻止固态聚集。使用原子力显微镜和 X 射线衍射的薄膜表征数据表明，通过按 1 < 2 < 3 的顺序增加空间体积来减少 PDI 聚集与结晶 TIPS-Pn 域的密度/尺寸的减小相关。对类似于 100 nm 溶液处理的 TIPS-Pn:PDI 共混薄膜进行瞬态吸收光谱分析，以表征电荷分离动力学。这些结果表明，TIPS-Pn 的选择性激发导致超快单线态裂变 ((1)*TIPS-Pn + TIPS-Pn -> 2 (3)*TIPS-Pn) 和从 (1)*TIPS-Pn 到 PDI 1-3 的电荷转移之间的竞争。随着 TIPS-Pn:PDI 1 -> 2 -> 3 系列中的共混膜变得更加均匀，电荷分离变得与单线态裂变具有竞争力。超快电荷分离形成双自由基离子对态 (1)(TIPS-Pn(+中心点)-PDI-中心点)，其经历自由基对系间窜越形成 (3)(TIPS-Pn(+中心点)-PDI-中心点)，然后经历电荷重组，产生 (3)*PDI 或 (3)*TIPS-Pn。从 (3)*PDI 到 TIPS-Pn 的能量转移也产生 (3)*TIPS-Pn。这些结果表明，多种途径产生 (3)*TIPS-Pn 态，因此基于该系统的 OPV 设计策略必须利用这种三重态进行电荷分离。
The photophysics and morphology of thin films of N,N-bis(2,6-diisopropylphenyl)perylene-3,4:9,10-bis(dicarboximide) (1) and the 1,7-diphenyl (2) and 1,7-bis(3,5-di-tert-butylphenyl) (3) derivatives blended with 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) were studied for their potential use as photoactive layers in organic photovoltaic (OPV) devices. Increasing the steric bulk of the 1,7-substituents of the perylene-3,4:9,10-bis(dicarboximide) (PDI) impedes aggregation in the solid state. Film characterization data using both atomic force microscopy and X-ray diffraction showed that decreasing the PDI aggregation by increasing the steric bulk in the order 1 < 2 < 3 correlates with a decrease in the density/size of crystalline TIPS-Pn domains. Transient absorption spectroscopy was performed on similar to 100 nm solution-processed TIPS-Pn:PDI blend films to characterize the charge separation dynamics. These results showed that selective excitation of the TIPS-Pn results in competition between ultrafast singlet fission ((1)*TIPS-Pn + TIPS-Pn -> 2 (3)*TIPS-Pn) and charge transfer from (1)*TIPS-Pn to PDIs 1-3. As the blend films become more homogeneous across the series TIPS-Pn:PDI 1 -> 2 -> 3, charge separation becomes competitive with singlet fission. Ultrafast charge separation forms the geminate radical ion pair state (1)(TIPS-Pn(+center dot)-PDI-center dot) that undergoes radical pair intersystem crossing to form (3)(TIPS-Pn(+center dot)-PDI-center dot), which then undergoes charge recombination to yield either (3)*PDI or (3)*TIPS-Pn. Energy transfer from (3)*PDI to TIPS-Pn also yields (3)*TIPS-Pn. These results show that multiple pathways produce the (3)*TIPS-Pn state, so that OPV design strategies based on this system must utilize this triplet state for charge separation.