TY - JOUR
T1 - Correlated In Situ Low-Frequency Noise and Impedance Spectroscopy Reveal Recombination Dynamics in Organic Solar Cells Using Fullerene and Non-Fullerene Acceptors
AU - Luck, Kyle A.
AU - Sangwan, Vinod K.
AU - Hartnett, Patrick E.
AU - Arnold, Heather N.
AU - Wasielewski, Michael R.
AU - Marks, Tobin J.
AU - Hersam, Mark C.
N1 - Funding Information:
This work was supported as part of the Argonne-Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0001059. The Institute for Sustainability and Energy at Northwestern (ISEN) provided partial equipment funding. K.A.L. acknowledges a graduate research fellowship from the National Science Foundation. H.N.A. acknowledges support from a NASA Space Technology Research Fellowship (NSTRF, No. NNX11AM87H). This work made use of the Keck-II facility of the NUANCE Center at Northwestern University, which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the NSF-MRSEC program (NSF DMR-1121262); the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois. The authors also thank N. D. Eastham and Prof. A. S. Dudnik for helpful discussions.
PY - 2017/12/22
Y1 - 2017/12/22
N2 - Non-fullerene acceptors based on perylenediimides (PDIs) have garnered significant interest as an alternative to fullerene acceptors in organic photovoltaics (OPVs), but their charge transport phenomena are not well understood, especially in bulk heterojunctions (BHJs). Here, charge transport and current fluctuations are investigated by performing correlated low-frequency noise and impedance spectroscopy measurements on two BHJ OPV systems, one employing a fullerene acceptor and the other employing a dimeric PDI acceptor. In the dark, these measurements reveal that PDI-based OPVs have a greater degree of recombination in comparison to fullerene-based OPVs. Furthermore, for the first time in organic solar cells, 1/f noise data are fit to the Kleinpenning model to reveal underlying current fluctuations in different transport regimes. Under illumination, 1/f noise increases by approximately four orders of magnitude for the fullerene-based OPVs and three orders of magnitude for the PDI-based OPVs. An inverse correlation is also observed between noise spectral density and power conversion efficiency. Overall, these results show that low-frequency noise spectroscopy is an effective in situ diagnostic tool to assess charge transport in emerging photovoltaic materials, thereby providing quantitative guidance for the design of next-generation solar cell materials and technologies.
AB - Non-fullerene acceptors based on perylenediimides (PDIs) have garnered significant interest as an alternative to fullerene acceptors in organic photovoltaics (OPVs), but their charge transport phenomena are not well understood, especially in bulk heterojunctions (BHJs). Here, charge transport and current fluctuations are investigated by performing correlated low-frequency noise and impedance spectroscopy measurements on two BHJ OPV systems, one employing a fullerene acceptor and the other employing a dimeric PDI acceptor. In the dark, these measurements reveal that PDI-based OPVs have a greater degree of recombination in comparison to fullerene-based OPVs. Furthermore, for the first time in organic solar cells, 1/f noise data are fit to the Kleinpenning model to reveal underlying current fluctuations in different transport regimes. Under illumination, 1/f noise increases by approximately four orders of magnitude for the fullerene-based OPVs and three orders of magnitude for the PDI-based OPVs. An inverse correlation is also observed between noise spectral density and power conversion efficiency. Overall, these results show that low-frequency noise spectroscopy is an effective in situ diagnostic tool to assess charge transport in emerging photovoltaic materials, thereby providing quantitative guidance for the design of next-generation solar cell materials and technologies.
KW - 1/f noise
KW - PBDTTT-EFT
KW - PCBM
KW - alternate acceptors
KW - organic photovoltaics
UR - http://www.scopus.com/inward/record.url?scp=85038426540&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85038426540&partnerID=8YFLogxK
U2 - 10.1002/adfm.201703805
DO - 10.1002/adfm.201703805
M3 - Article
AN - SCOPUS:85038426540
VL - 27
JO - Advanced Functional Materials
JF - Advanced Functional Materials
SN - 1616-301X
IS - 48
M1 - 1703805
ER -