skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory

Abstract

The efficiency of bulk heterojunction (BHJ) organic photovoltaics is sensitive to the morphology of the fullerene network that transports electrons through the device. This sensitivity makes it difficult to distinguish the contrasting roles of local electron mobility (how easily electrons can transfer between neighboring fullerene molecules) and macroscopic electron mobility (how well-connected is the fullerene network on device length scales) in solar cell performance. In this work, a combination of density functional theory (DFT) calculations, flash-photolysis time-resolved microwave conductivity (TRMC) experiments, and space-charge-limit current (SCLC) mobility estimates are used to examine the roles of local and macroscopic electron mobility in conjugated polymer/fullerene BHJ photovoltaics. The local mobility of different pentaaryl fullerene derivatives (so-called ‘shuttlecock’ molecules) is similar, so that differences in solar cell efficiency and SCLC mobilities result directly from the different propensities of these molecules to self-assemble on macroscopic length scales. These experiments and calculations also demonstrate that the local mobility of phenyl-C60 butyl methyl ester (PCBM) is an order of magnitude higher than that of other fullerene derivatives, explaining why PCBM has been the acceptor of choice for conjugated polymer BHJ devices even though it does not form an optimal macroscopic network. The DFT calculations indicate that PCBM'smore » superior local mobility comes from the near-spherical nature of its molecular orbitals, which allow strong electronic coupling between adjacent molecules. In combination, DFT and TRMC techniques provide a tool for screening new fullerene derivatives for good local mobility when designing new molecules that can improve on the macroscopic electron mobility offered by PCBM.« less

Authors:
 [1];  [1];  [1];  [1];  [2];  [1];  [1];  [1];  [1];  [2];  [1];  [1]
  1. Univ. of California, Los Angeles, CA (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1227050
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Advanced Functional Materials (Online)
Additional Journal Information:
Journal Volume: 24; Journal Issue: 6; Journal ID: ISSN 1616-3028
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; Environmental Molecular Sciences Laboratory

Citation Formats

Aguirre, Jordan C., Arntsen, Christopher D., Hernandez, Samuel, Huber, Rachel, Nardes, Alexandre M., Halim, Merissa, Kilbride, Daniel, Rubin, Yves, Tolbert, Sarah H., Kopidakis, Nikos, Schwartz, Benjamin J., and Neuhauser, Daniel. Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory. United States: N. p., 2013. Web. doi:10.1002/adfm.201301757.
Aguirre, Jordan C., Arntsen, Christopher D., Hernandez, Samuel, Huber, Rachel, Nardes, Alexandre M., Halim, Merissa, Kilbride, Daniel, Rubin, Yves, Tolbert, Sarah H., Kopidakis, Nikos, Schwartz, Benjamin J., & Neuhauser, Daniel. Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory. United States. doi:10.1002/adfm.201301757.
Aguirre, Jordan C., Arntsen, Christopher D., Hernandez, Samuel, Huber, Rachel, Nardes, Alexandre M., Halim, Merissa, Kilbride, Daniel, Rubin, Yves, Tolbert, Sarah H., Kopidakis, Nikos, Schwartz, Benjamin J., and Neuhauser, Daniel. Mon . "Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory". United States. doi:10.1002/adfm.201301757.
@article{osti_1227050,
title = {Understanding Local and Macroscopic Electron Mobilities in the Fullerene Network of Conjugated Polymer-based Solar Cells. Time-Resolved Microwave Conductivity and Theory},
author = {Aguirre, Jordan C. and Arntsen, Christopher D. and Hernandez, Samuel and Huber, Rachel and Nardes, Alexandre M. and Halim, Merissa and Kilbride, Daniel and Rubin, Yves and Tolbert, Sarah H. and Kopidakis, Nikos and Schwartz, Benjamin J. and Neuhauser, Daniel},
abstractNote = {The efficiency of bulk heterojunction (BHJ) organic photovoltaics is sensitive to the morphology of the fullerene network that transports electrons through the device. This sensitivity makes it difficult to distinguish the contrasting roles of local electron mobility (how easily electrons can transfer between neighboring fullerene molecules) and macroscopic electron mobility (how well-connected is the fullerene network on device length scales) in solar cell performance. In this work, a combination of density functional theory (DFT) calculations, flash-photolysis time-resolved microwave conductivity (TRMC) experiments, and space-charge-limit current (SCLC) mobility estimates are used to examine the roles of local and macroscopic electron mobility in conjugated polymer/fullerene BHJ photovoltaics. The local mobility of different pentaaryl fullerene derivatives (so-called ‘shuttlecock’ molecules) is similar, so that differences in solar cell efficiency and SCLC mobilities result directly from the different propensities of these molecules to self-assemble on macroscopic length scales. These experiments and calculations also demonstrate that the local mobility of phenyl-C60 butyl methyl ester (PCBM) is an order of magnitude higher than that of other fullerene derivatives, explaining why PCBM has been the acceptor of choice for conjugated polymer BHJ devices even though it does not form an optimal macroscopic network. The DFT calculations indicate that PCBM's superior local mobility comes from the near-spherical nature of its molecular orbitals, which allow strong electronic coupling between adjacent molecules. In combination, DFT and TRMC techniques provide a tool for screening new fullerene derivatives for good local mobility when designing new molecules that can improve on the macroscopic electron mobility offered by PCBM.},
doi = {10.1002/adfm.201301757},
journal = {Advanced Functional Materials (Online)},
issn = {1616-3028},
number = 6,
volume = 24,
place = {United States},
year = {2013},
month = {9}
}