@article{75c2f3a1878d4f92b3d7852115e21bfc,
title = "Enhanced Light Absorption in Fluorinated Ternary Small-Molecule Photovoltaics",
abstract = "Using small-molecule donor (SMD) semiconductors in organic photovoltaics (OPVs) has historically afforded lower power conversion efficiencies (PCEs) than their polymeric counterparts. The PCE difference is attributed to shorter conjugated backbones, resulting in reduced intermolecular interactions. Here, a new pair of SMDs is synthesized based on the diketopyrrolopyrrole-benzodithiophene-diketopyrrolopyrrole (BDT-DPP2) skeleton but having fluorinated and fluorine-free aromatic side-chain substituents. Ternary OPVs having varied ratios of the two SMDs with PC61BM as the acceptor exhibit tunable open-circuit voltages (Vocs) between 0.833 and 0.944 V due to a fluorination-induced shift in energy levels and the electronic {"}alloy{"} formed from the miscibility of the two SMDs. A 15% increase in PCE is observed at the optimal ternary SMD ratio, with the short-circuit current density (Jsc) significantly increased to 9.18 mA/cm2. The origin of Jsc enhancement is analyzed via charge generation, transport, and diffuse reflectance measurements, and is attributed to increased optical absorption arising from a maximum in film crystallinity at this SMD ratio, observed by grazing incidence wide-angle X-ray scattering.",
author = "Eastham, {Nicholas D.} and Dudnik, {Alexander S.} and Boris Harutyunyan and Aldrich, {Thomas J.} and Leonardi, {Matthew J.} and Manley, {Eric F.} and Butler, {Melanie R.} and Tobias Harschneck and Ratner, {Mark A.} and Chen, {Lin X.} and Bedzyk, {Michael J.} and Melkonyan, {Ferdinand S.} and Antonio Facchetti and Chang, {Robert P.H.} and Marks, {Tobin J.}",
note = "Funding Information: This research was supported in part by the Argonne− Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001059 (N.D.E., R.P.H.C., and T.J.M. for device fabrication and characterization, B.H., M.J.B., and L.X.C. for X-ray characterization) and by AFOSR Grant FA9550-08-1-0331 (A.F.). Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. This work made use of the EPIC, Keck-II, and/or SPID facilities of Northwestern University{\textquoteright}s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. A.S.D. thanks the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry for a fellowship. T.J.A. and M.R.B. thank the NSF for predoctoral fellowships, and M.J.L thanks the NDSEG for a predoctoral fellowship. F.S.M. was supported by Award 70NANB14H012 from the U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD), and E.F.M. was supported by Qatar NPRP Grant 7-286-1-046. Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",
year = "2017",
month = jul,
day = "14",
doi = "10.1021/acsenergylett.7b00486",
language = "English (US)",
volume = "2",
pages = "1690--1697",
journal = "ACS Energy Letters",
issn = "2380-8195",
publisher = "American Chemical Society",
number = "7",
}
