title: Photoinduced Charge-Carrier Generation in Epitaxial MOF Thin Films: High Efficiency as a Result of an Indirect Electronic Band Gap?
abstract: For inorganic semiconductors crystalline order leads to a band structure which gives rise to drastic differences to the disordered material. An example is the presence of an indirect band gap. For organic semiconductors such effects are typically not considered, since the bands are normally flat, and the band-gap therefore is direct. Herein we show results from electronic structure calculations demonstrating that ordered arrays of porphyrins reveal a small dispersion of occupied and unoccupied bands leading to the formation of a small indirect band gap. We demonstrate herein that such ordered structures can be fabricated by liquid-phase epitaxy and that the corresponding crystalline organic semiconductors exhibit superior photophysical properties, including large charge-carrier mobility and an unusually large charge-carrier generation efficiency. We have fabricated a prototype organic photovoltaic device based on this novel material exhibiting a remarkable efficiency.
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany). jinxuan.liu@dlut.edu.cn.|Institute of Artificial Photosynthesis, State Key Laboratory of Fine Chemicals, Dalian University of Technology (China). jinxuan.liu@dlut.edu.cn.
authors.forename: Jinxuan
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany).
authors.forename: Wencai
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany).
authors.forename: Jianxi
authors.initials: J
authors.lastname: Liu
authors.affiliation: Institute of Microstructure Technology, Karlsruhe Institute of Technology (Germany).
authors.forename: Ian
authors.initials: I
authors.lastname: Howard
authors.affiliation: Institute for Applied Materials, Karlsruhe Institute of Technology (Germany).
authors.forename: Goran
authors.initials: G
authors.lastname: Kilibarda
authors.affiliation: Institute for Applied Materials, Karlsruhe Institute of Technology (Germany).
authors.forename: Sabine
authors.initials: S
authors.lastname: Schlabach
authors.affiliation: Engineering and Science, Jacobs-University Bremen, Department of Physics and Earth Science, 28759 Bremen (Germany).
authors.forename: Damien
authors.initials: D
authors.lastname: Coupry
authors.affiliation: Engineering and Science, Jacobs-University Bremen, Department of Physics and Earth Science, 28759 Bremen (Germany).
authors.forename: Matthew
authors.initials: M
authors.lastname: Addicoat
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University (Japan).
authors.forename: Satoru
authors.initials: S
authors.lastname: Yoneda
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University (Japan).
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsutsui
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University (Japan).
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Sakurai
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University (Japan).
authors.forename: Shu
authors.initials: S
authors.lastname: Seki
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany).
authors.forename: Zhengbang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany).
authors.forename: Peter
authors.initials: P
authors.lastname: Lindemann
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany).
authors.forename: Engelbert
authors.initials: E
authors.lastname: Redel
authors.affiliation: Engineering and Science, Jacobs-University Bremen, Department of Physics and Earth Science, 28759 Bremen (Germany).
authors.forename: Thomas
authors.initials: T
authors.lastname: Heine
authors.affiliation: Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen (Germany). christof.woell@kit.edu.
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
keywords: metal-organic frameworks; photocarrier mobility; photovoltaic device; porphyrin; semiconductors