@article{5e4703a95a534c929344abe5265ec3d1,
title = "Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells",
abstract = "Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.",
author = "Yu Zhong and Trinh, {M. Tuan} and Rongsheng Chen and Purdum, {Geoffrey E.} and Khlyabich, {Petr P.} and Melda Sezen and Seokjoon Oh and Haiming Zhu and Brandon Fowler and Boyuan Zhang and Wei Wang and Nam, {Chang Yong} and Sfeir, {Matthew Y.} and Black, {Charles T.} and Steigerwald, {Michael L.} and Loo, {Yueh Lin} and Fay Ng and Zhu, {X. Y.} and Colin Nuckolls",
note = "Funding Information: Primary support for this project was provided by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, US Department of Energy (DOE) under award number DE-FG02-01ER15264. X.Y.Z. acknowledges support by the US National Science Foundation grant DMR 1321405. This research used resources of the Center for Functional Nanomaterials, which is a US DOE Office of Science User Facility, at Brookhaven National Laboratory under contract number DE-SC0012704. Portions of this work was conducted at the Cornell High Energy Synchrotron Source (CHESS), which is supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF awards DMR-0936384 and DMR-1332208. G.E.P. acknowledges Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. We thank Columbia University{\textquoteright}s Shared Materials Characterization Lab for use of the equipment essential to the research. Publisher Copyright: {\textcopyright} 2015 Macmillan Publishers Limited. All rights reserved.",
year = "2015",
month = sep,
day = "18",
doi = "10.1038/ncomms9242",
language = "English (US)",
volume = "6",
journal = "Nature Communications",
issn = "2041-1723",
publisher = "Nature Publishing Group",
}