Correlation between Exciton Lifetime Distribution and Morphology of Bulk Heterojunction Films after Solvent Annealing

Jen-Hsien, Huang and Kuang, Chieh Li and Fang-Chung, Chen and Yu-Sheng, Hsiao and Kekuda, Dhananjaya and Peilin, Chen and Hong-Cheu , Lin and Kuo, Chuan Ho and Chih, Wei Chu (2010) Correlation between Exciton Lifetime Distribution and Morphology of Bulk Heterojunction Films after Solvent Annealing. Journal of Physical Chemistry, 114 (19). pp. 9062-9069.

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Abstract

We have synthesized a low-bandgap polymer, bithiazole-based polymer (PCPDTTBT) containing cyclopentadithiophene and thiophene units, and studied its opticophysical properties and morphologies in bulk heterojunction films after annealing. We used confocal optical microscopy in conjunction with a fluorescence module to record exciton lifetime images within photoactive layers of PCPDTTBT and [6,6]-phenyl-C61- butyric acid methyl ester (PCBM). These images, which were consistent with those recorded using atomic force microscopy and transmission electron microscopy, revealed that phase separation of PCPDTTBT and PCBM occurred during slow solvent evaporation. This phase separation not only provided bicontinuous pathways for carrier transport to the respective electrodes but also enhanced the degree of polymer chain stacking, thereby improving the absorption and balancing the electron and hole mobilities. We tested the performance of solar cells incorporating PCPDTTBT and various fullerene derivatives. Under AM 1.5 G illumination (100 mW cm-2), a PCPDTTBT/bisPCBM-based solar cell exhibited a power conversion efficiency of 3.8%, with a short circuit current of 7.3 mA cm-2, an open circuit voltage of 0.88 V, and a fill factor of 59.1%.

Item Type: Article
Subjects: Engineering > MIT Manipal > Physics
Depositing User: MIT Library
Date Deposited: 16 Oct 2013 06:48
Last Modified: 16 Oct 2013 06:48
URI: http://eprints.manipal.edu/id/eprint/137490

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