Quantitative Analyses of Competing Photocurrent Generation Mechanisms in Fullerene-Based Organic Photovoltaics

详细信息    查看全文

• 作者：Liang Xu ; Jian Wang ; Manuel de Anda Villa ; Trey B. Daunis ; Yun-Ju Lee ; Anton V. Malko ; Julia W. P. Hsu
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 4, 2016
• 年：2016
• 卷：120
• 期：30
• 页码：16470-16477
• 全文大小：508K
• 年卷期：0
• ISSN：1932-7455

文摘

The performance of fullerene-based organic photovoltaic devices (OPVs) with low donor concentrations is not limited by the trade-off between short-circuit current density (J_sc) and open-circuit voltage (V_oc), unlike bulk heterojunction OPVs. While the high V_oc in this novel type of OPVs has been studied, here we investigate the mechanisms that govern J_sc, which are not well understood. Three mechanisms, diffusion limited exciton relaxation, geminate recombination during exciton dissociation, and nongeminate recombination during charge transport, are studied analytically by combining various experimental techniques and transfer matrix simulation. We find that exciton dissociation at donor/acceptor interfaces is the dominant factor to produce high J_sc, and at low P3HT concentrations exciton relaxation limits photocurrent generation. With more P3HT inclusion, the creation of interfaces promotes exciton dissocation but also reduces fullerene crystallinity, weakening the driving force for charge separation, and introduces nongeminate recombination sites. Quantitative analyses show that the magnitude of measured J_sc and the donor concentration dependence are well accounted for by these three competing mechanisms.