title: Interplay between Interfacial Structures and Device Performance in Organic Solar Cells: A Case Study with the Low Work Function Metal, Calcium.
abstract: A better understanding of how interfacial structure affects charge carrier recombination would benefit the development of highly efficient organic photovoltaic (OPV) devices. In this paper, transient photovoltage (TPV) and charge extraction (CE) measurements are used in combination with synchrotron radiation photoemission spectroscopy (SRPES) to gain insight into the correlation between interfacial properties and device performance. OPV devices based on PCDTBT/PC71BM with a Ca interlayer were studied as a reference system to investigate the interfacial effects on device performance. Devices with a Ca interlayer exhibit a lower recombination than devices with only an Al cathode at a given charge carrier density (n). In addition, the interfacial band structures indicate that the strong dipole moment produced by the Ca interlayer can facilitate the extraction of electrons and drive holes away from the cathode/polymer interface, resulting in beneficial reduction in interfacial recombination losses. These results help explain the higher efficiencies of devices made with Ca interlayers compared to that without the Ca interlayer.
authors.affiliation: National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China , Hefei, Anhui 230029, People's Republic of China.|Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.|Hefei Science Center, Chinese Academy of Sciences , Hefei, Anhui 230029, People's Republic of China.
authors.forename: Huanxin
authors.initials: H
authors.lastname: Ju
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Kristina M
authors.initials: KM
authors.lastname: Knesting
authors.affiliation: National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China , Hefei, Anhui 230029, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China , Hefei, Anhui 230029, People's Republic of China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Pan
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Chia-Hsin
authors.initials: CH
authors.lastname: Wang
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Yaw-Wen
authors.initials: YW
authors.lastname: Yang
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: David S
authors.initials: DS
authors.lastname: Ginger
authors.affiliation: National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China , Hefei, Anhui 230029, People's Republic of China.|Hefei Science Center, Chinese Academy of Sciences , Hefei, Anhui 230029, People's Republic of China.
authors.forename: Junfa
authors.initials: J
authors.lastname: Zhu
keywords: band structures; charge carrier recombination; interface; organic solar cells; transient photovoltage