Increased Exciton Dipole Moment Translates into Charge-Transfer Excitons in Thiophene-Fluorinated Low-Bandgap Polymers for Organic Photovoltaic Applications
Increased Exciton Dipole Moment Translates into Charge-Transfer Excitons in Thiophene-Fluorinated Low-Bandgap Polymers for Organic Photovoltaic Applications
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DOI：
10.1021/acs.chemmater.5b02948
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发表时间：
2015-12-08
影响因子：
8.6
通讯作者：
Heeney, Martin
中科院分区：
文献类型：
--
作者：
Collado-Fregoso, Elisa;Boufflet, Pierre;Heeney, Martin
在这项研究中，我们调查的作用，噻吩并噻吩在低能带隙聚合物的有机光伏应用。我们采用理论和实验相结合的方法来研究电荷产生和复合动力学，以及它们与共混物微观结构和聚合物偶极矩的相关性。我们发现，在激子形成时，这是与电荷转移激子的外观，从超快瞬态吸收研究证明，在偶极矩的变化增加的结果。氟化也导致更小，但更纯的域，证明了原子力显微镜和共振软X射线散射，并与光致发光猝灭测量的协议。这种薄膜形态的变化与非偕胺酸盐复合损失的适度延迟相关。有效的电荷产生和更慢的复合可能是氟化聚合物/富勒烯器件中增强的器件效率的部分原因。
In this study, we investigate the role of thiophene fluorination in a low-bandgap polymer for organic photovoltaic applications. We use a combined theoretical and experimental approach to investigate charge generation and recombination dynamics, and their correlation with blend microstructure and polymer dipole moment. We find that fluorination results in an increased change in the dipole moment upon exciton formation, which is correlated with the appearance of charge-transfer excitons, as evidenced from ultrafast transient absorption studies. Fluorination also results in smaller yet purer domains, evidenced by atomic force microscopy and resonant soft X-ray scattering, and in agreement with photoluminescence quenching measurements. This change in film morphology is correlated with a modest retardation of nongeminate recombination losses. The efficient charge generation and slower recombination are likely to be partly responsible for the enhanced device efficiency in the fluorinated polymer/fullerene devices.