[15p-1F-1~14] 12.5 Organic solar cells

[15p-1F-1] [Young Scientist Presentation Award Speech] Dominant Effects of First Monolayer Energetics at Donor/Acceptor Interfaces on Charge Separation and Recombination Processes

〇Seiichiro Izawa¹, Kyohei Nakano¹, Kaori Suzuki¹, Kazuhito Hashimoto², Keisuke Tajima^1,3 (1.RIKEN CEMS, 2.Tokyo Univ., 3.PRESTO)

Keywords:Organic photovoltaics,Donor/acceptor interface,Charge recombination

Interfacial donor/acceptor (D/A) structures that enable efficient charge separation and suppress charge recombination are important for enhancing organic photovoltaic (OPV) device performance. Here we report the manipulation of energy levels of the first monolayer at D/A interfaces in planar heterojunction OPVs by using molecular self-organization. A “cascade” energy landscape, in which the first monolayer of the acceptor at the interface has a higher energy level, allowed thermal activation-free charge generation by photoirradiation. The Coulomb binding energy of the interfacial charge transfer state was decreased and the bimolecular charge recombination was greatly suppressed. These resulted in a higher open-circuit voltage and fill factor without losing the photocurrent generation from the donor absorption. Our results demonstrate that the energetics of the first monolayer at the donor/acceptor interfaces strongly affect the photophysics in organic photovoltaic devices.