title: Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.
abstract: In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; Argonne Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Nanjia
authors.initials: N
authors.lastname: Zhou
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Myung-Gil
authors.initials: MG
authors.lastname: Kim
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Stephen
authors.initials: S
authors.lastname: Loser
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Jeremy
authors.initials: J
authors.lastname: Smith
authors.affiliation: Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan;
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yoshida
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; Argonne Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Xugang
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Charles
authors.initials: C
authors.lastname: Song
authors.affiliation: Department of Physics, Northwestern University, Evanston, IL 60208;
authors.forename: Hosub
authors.initials: H
authors.lastname: Jin
authors.affiliation: Materials Department, Polyera Corporation, Skokie, IL 60077.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208;
authors.forename: Seok Min
authors.initials: SM
authors.lastname: Yoon
authors.affiliation: Department of Physics, Northwestern University, Evanston, IL 60208;
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Freeman
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; Argonne Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208; t-marks@northwestern.edu r-chang@northwestern.edu a-facchetti@northwestern.edu.
authors.forename: Robert P H
authors.initials: RP
authors.lastname: Chang
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208; Materials Department, Polyera Corporation, Skokie, IL 60077 t-marks@northwestern.edu r-chang@northwestern.edu a-facchetti@northwestern.edu.
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208; Argonne Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208; Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, IL 60208; t-marks@northwestern.edu r-chang@northwestern.edu a-facchetti@northwestern.edu.
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks
keywords: amorphous oxide; interface; interfacial layers; photovoltaic