Charge Recombination in P3HT/PC70BM Composite Studied by Light-Induced EPR

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• 作者：Ekaterina A. Lukina ; Mikhail N. Uvarov ; Leonid V. Kulik
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 14, 2014
• 年：2014
• 卷：118
• 期：32
• 页码：18307-18314
• 全文大小：381K
• ISSN：1932-7455

文摘

A composite of conductive polythiophene P3HT and soluble fullerene derivative PC₇₀BM (the material widely used as the active layer in organic photovoltaics devices) was studied by light-induced EPR (LEPR). In contrast to P3HT/PC₆₀BM composite, LEPR signal in P3HT/PC₇₀BM can be detected in a wide temperature range up to room temperature. This signal was attributed to charge carriers P3HT⁺ and PC₇₀BM^{鈥?/sup>. The dependence of the intensity of LEPR signal on light intensity and the decay of LEPR signal upon switching light off are interpreted in frame of trap-limited bimolecular recombination model with finite rate of back electron transfer in [P3HT+ PC₇₀BM鈥?/sup>] encounter complex at polymer鈥揻ullerene interface. The apparent recombination order was found to be close to p = 3.5 for the temperature range from 100 K to room temperature. For temperatures above 150 K Arrhenius behavior of effective recombination rate constant was obtained with the activation energy E_a = 0.16 卤 0.01 eV, which is larger than analogous values for P3HT/PC₆₀BM reported previously. This difference is attributed to the change of polymer/fullerene interface induced by the replacement of PC₆₀BM by PC₇₀BM.}