Abstract
The rational design of new high performance materials for organic photovoltaic (OPV) applications is largely inhibited by a lack of design rules for materials that have slow bimolecular charge recombination. Due to the complex device physics present in OPVs, rigorous and reliable measurement techniques for charge transport and charge recombination are needed to construct improved physical models that can guide materials development and discovery. Here, we develop a new technique called impedance-photocurrent device analysis (IPDA) to quantitatively characterize the competition between charge extraction and charge recombination under steady state operational conditions. The measurements are performed on actual lab scale solar cells, have mild equipment requirements, and can be integrated into normal device fabrication and testing workflows. We perform IPDA tests on a broad set of devices with varying polymer:fullerene blend chemistry and processing conditions. Results from the IPDA technique exhibit significantly improved reliability and self-consistency compared to the open-circuit voltage decay technique (OCVD). IPDA measurements also reveal a significant negative electric field dependence of the bimolecular recombination coefficient in high fill factor devices, a finding which is inaccessible to most other common techniques and indicates that many of these techniques may overestimate the value that is most relevant for describing device performance. Future work utilizing IPDA to build structure-property relationships for bimolecular recombination will lead to enhanced design rules for creating efficient OPVs that are suitable for commercialization.
Original language | English |
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Pages (from-to) | 3019-3032 |
Number of pages | 14 |
Journal | Energy and Environmental Science |
Volume | 11 |
Issue number | 10 |
DOIs | |
Publication status | Published - 2018 Oct |
Bibliographical note
Funding Information:M. C. H. and T.-Q. N. acknowledge primary funding by the Office of Naval Research (ONR) Award No. N00014-14-1-0580. M. C. H. acknowledges partial support by financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). T. O. acknowledges support from the MEXT-Supported Program for the Strategic Research Foundation at Private Universities (2014–2018) and Kindai University. M. A. U. and H. Y. W. are grateful for financial support from the NRF of Korea (2015M1A2A2057506). M. C. H. thanks Dr Alexander Mikhailovsky and Dr Samuel D. Collins for assistance with building and testing the measurement setups.
Funding Information:
M. C. H. and T.-Q. N. acknowledge primary funding by the Office of Naval Research (ONR) Award No. N00014-14-1-0580. M. C. H. acknowledges partial support by financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). T. O. acknowledges support from the MEXT-Supported Program for the Strategic Research Foundation at Private Universities (2014-2018) and Kindai University. M. A. U. and H. Y. W. are grateful for financial support from the NRF of Korea (2015M1A2A2057506). M. C. H. thanks Dr Alexander Mikhailovsky and Dr Samuel D. Collins for assistance with building and testing the measurement setups.
Publisher Copyright:
© 2018 The Royal Society of Chemistry.
ASJC Scopus subject areas
- Environmental Chemistry
- Renewable Energy, Sustainability and the Environment
- Nuclear Energy and Engineering
- Pollution