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Title: Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%

Abstract

Cascade heterojunction (CHJ) organic solar cells have recently emerged as an alternative to conventional bulk heterojunctions and series-connected tandems due to their significant promise for high internal quantum efficiency (IQE) and broad spectral coverage. However, CHJ devices thus far have also exhibited poor fill factor (FF), resulting in minimal enhancements (or even decreases) in power conversion efficiency (PCE) when compared with single heterojunction (SHJ) cells. In this study, the major variables controlling the CHJ maximum power point and FF are determined using a combinatorial approach. By matching the maximum power point voltage (VMPP) of the constituent parallel-connected heterojunctions (subjunctions) and minimizing the injection barriers intrinsic to CHJs, high FF and PCE can be achieved. Optimized CHJ devices are demonstrated with >99% IQE in the interlayer and a 46% increase in PCE compared to a SHJ reference (4.1% versus 2.8%). Devices with a transparent exciton dissociation layer (EDL)/interlayer/acceptor structure are employed, such that each CHJ has absorption efficiency identical to its interlayer/acceptor SHJ counterpart. Using these results, a clear map of performance as a function of material parameters is developed, providing straightforward, universal design rules to guide future engineering of molecules and layer architectures for CHJ organic photovoltaic devices.

Authors:
 [1];  [1];  [1];  [1];  [2];  [1];  [1];  [1]
  1. Materials Science and Engineering, University of Michigan, Ann Arbor MI 48109 USA
  2. Macromolecular Science and Engineering, University of Michigan, Ann Arbor MI 48109 USA
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Solar and Thermal Energy Conversion (CSTEC)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1384377
DOE Contract Number:  
SC0000957
Resource Type:
Journal Article
Journal Name:
Advanced Energy Materials
Additional Journal Information:
Journal Volume: 4; Journal Issue: 13; Related Information: CSTEC partners with University of Michigan (lead); Kent State University; Journal ID: ISSN 1614-6832
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; solar (photovoltaic), solar (thermal), phonons, thermal conductivity, thermoelectric, electrodes - solar, defects, charge transport, materials and chemistry by design, optics, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Barito, Adam, Sykes, Matthew E., Huang, Bingyuan, Bilby, David, Frieberg, Bradley, Kim, Jinsang, Green, Peter F., and Shtein, Max. Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%. United States: N. p., 2014. Web. doi:10.1002/aenm.201400216.
Barito, Adam, Sykes, Matthew E., Huang, Bingyuan, Bilby, David, Frieberg, Bradley, Kim, Jinsang, Green, Peter F., & Shtein, Max. Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%. United States. doi:10.1002/aenm.201400216.
Barito, Adam, Sykes, Matthew E., Huang, Bingyuan, Bilby, David, Frieberg, Bradley, Kim, Jinsang, Green, Peter F., and Shtein, Max. Sat . "Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%". United States. doi:10.1002/aenm.201400216.
@article{osti_1384377,
title = {Universal Design Principles for Cascade Heterojunction Solar Cells with High Fill Factors and Internal Quantum Efficiencies Approaching 100%},
author = {Barito, Adam and Sykes, Matthew E. and Huang, Bingyuan and Bilby, David and Frieberg, Bradley and Kim, Jinsang and Green, Peter F. and Shtein, Max},
abstractNote = {Cascade heterojunction (CHJ) organic solar cells have recently emerged as an alternative to conventional bulk heterojunctions and series-connected tandems due to their significant promise for high internal quantum efficiency (IQE) and broad spectral coverage. However, CHJ devices thus far have also exhibited poor fill factor (FF), resulting in minimal enhancements (or even decreases) in power conversion efficiency (PCE) when compared with single heterojunction (SHJ) cells. In this study, the major variables controlling the CHJ maximum power point and FF are determined using a combinatorial approach. By matching the maximum power point voltage (VMPP) of the constituent parallel-connected heterojunctions (subjunctions) and minimizing the injection barriers intrinsic to CHJs, high FF and PCE can be achieved. Optimized CHJ devices are demonstrated with >99% IQE in the interlayer and a 46% increase in PCE compared to a SHJ reference (4.1% versus 2.8%). Devices with a transparent exciton dissociation layer (EDL)/interlayer/acceptor structure are employed, such that each CHJ has absorption efficiency identical to its interlayer/acceptor SHJ counterpart. Using these results, a clear map of performance as a function of material parameters is developed, providing straightforward, universal design rules to guide future engineering of molecules and layer architectures for CHJ organic photovoltaic devices.},
doi = {10.1002/aenm.201400216},
journal = {Advanced Energy Materials},
issn = {1614-6832},
number = 13,
volume = 4,
place = {United States},
year = {2014},
month = {5}
}

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