Charge Carrier Dynamics of Vapor-Deposited Small-Molecule/Fullerene Organic Solar Cells

• Published in: Journal of the American Chemical Society Vol. 135; no. 24; pp. 8790 - 8793
• Main Authors: Chang, Angela Y, Chen, Yi-Hong, Lin, Hao-Wu, Lin, Li-Yen, Wong, Ken-Tsung, Schaller, Richard D
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19.06.2013
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja403056y

Although small-molecule organic solar cells (SMOSCs) have shown increasingly promising prospects as a source of solar power, there have been few studies concerning the photophysics of these systems. Here, we report the time scale and efficiency of charge separation and recombination in a vapor-deposited SMOSC material that produces 5.81% power conversion efficiency. Transient absorption and time-resolved photoluminescence (trPL) studies of thin film blends comprising DTDCTB, a narrow-band gap electron donor, and either C60 or C70 as an electron acceptor show that charge separation occurs in ∼100 fs, while charge recombination takes place over sub-ns and ns time scales. trPL indicates a donor electron–hole pair lifetime of ∼33 ps in the neat film and reveals that ∼20% of donors fail to charge separate in donor–acceptor mixed films, likely owing to some spatially extended donor-rich regions that interact poorly with acceptors. Our results suggest that morphological manipulations of this material could further improve device efficiency.