Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
J Am Chem Soc. 2014 Jan 29;136(4):1472-82. doi: 10.1021/ja410340g. Epub 2014 Jan 17.
PBDTTPD is one of the best conjugated polymers for solar cell applications (up to 8.5% efficiency). We have investigated the dynamics of charge generation in the blend with fullerene (PCBM) and addressed highly relevant topics such as the role of bulk heterojunction structure, fullerene excitation, and excess energy. We show that there are multiple charge separation pathways. These include electron transfer from photoexcited polymer, hole transfer from photoexcited PCBM, prompt (<100 fs) charge generation in intimately mixed polymer:fullerene regions (which can occur from hot states), as well as slower electron and hole transfer from excitons formed in pure PBDTTPD or PCBM domains (diffusion to an interface is necessary). Very interestingly, all the charge separation pathways are highly efficient. For example, the yield of long-lived carriers is not significantly affected by the excitation wavelength, although this changes the fraction of photons absorbed by PCBM and the amount of excess energy brought to the system. Overall, the favorable properties of the PBDTTPD:PCBM blend in terms of morphology and exciton delocalization allow excellent charge generation in all circumstances and strongly contribute to the high photovoltaic performance of the blend.
PBDTTPD 是用于太阳能电池应用的最佳共轭聚合物之一（效率高达 8.5%）。我们研究了与富勒烯（PCBM）共混物中的电荷产生动力学，并解决了一些高度相关的问题，例如体异质结结构、富勒烯激发和过剩能量的作用。我们表明存在多种电荷分离途径。这些途径包括：从光激发聚合物转移电子，从光激发 PCBM 转移空穴，在紧密混合的聚合物：富勒烯区域中发生的快速（<100 fs）电荷产生（这可能来自热态），以及从纯 PBDTTPD 或 PCBM 域中形成的激子中较慢的电子和空穴转移（扩散到界面是必要的）。非常有趣的是，所有的电荷分离途径都非常高效。例如，长寿命载流子的产率不受激发波长的显著影响，尽管这会改变 PCBM 吸收的光子分数和传递给系统的过剩能量。总体而言，PBDTTPD：PCBM 共混物在形态和激子离域方面的有利性质允许在所有情况下都能产生优异的电荷，并对共混物的高光伏性能做出了重要贡献。
