title: Effects of Contact-Induced Doping on the Behaviors of Organic Photovoltaic Devices.
abstract: Substrates can significantly affect the electronic properties of organic semiconductors. In this paper, we report the effects of contact-induced doping, arising from charge transfer between a high work function hole extraction layer (HEL) and the organic active layer, on organic photovoltaic device performance. Employing a high work function HEL is found to increase doping in the active layer and decrease photocurrent. Combined experimental and modeling investigations reveal that higher doping increases polaron-exciton quenching and carrier recombination within the field-free region. Consequently, there exists an optimal HEL work function that enables a large built-in field while keeping the active layer doping low. This value is found to be ~0.4 eV larger than the pinning level of the active layer material. These understandings establish a criterion for optimal design of the HEL when adapting a new active layer system and can shed light on optimizing performance in other organic electronic devices.
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Liang
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Yun-Ju
authors.initials: YJ
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Manuel
authors.initials: M
authors.lastname: De Anda Villa
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Anton V
authors.initials: AV
authors.lastname: Malko
authors.affiliation: Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Julia W P
authors.initials: JW
authors.lastname: Hsu
keywords: Fermi level pinning; capacitance−voltage; charge transfer; polaron−exciton quenching; recombination