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Title: Control of morphology and function of low band gap polymer–bis-fullerene mixed heterojunctions in organic photovoltaics with selective solvent vapor annealing

Abstract

We reported how by replacing PCBM with a bis-adduct fullerene (i.e. ICBA) we significantly improve the open circuit voltage (VOC) and power conversion efficiency (PCE) in P3HT bulk heterojunctions. But, for the most promising low band-gap polymer (LBP) systems, replacing PCBM with ICBA results in very poor shortcircuit current (JSC) and PCE although the VOC is significantly improved. Therefore, in this work, we have completed small angle neutron scattering and neutron reflectometry experiments to study the impact of post-deposition solvent annealing (SA) with control of solvent quality on the morphology and performance of LBP bis-fullerene BHJ photovoltaics. Our results show that SA in a solvent that is selective for the LBP results in a depletion of bis-fullerene near the air surface, which limits device performance. SA in a solvent vapor which has similar solubility for polymer and bis-fullerene results in a higher degree of polymer ordering, bis-fullerene phase separation, and segregation of the bis-fullerene to the air surface, which facilitates charge transport and increases power conversion efficiency (PCE) by 100%. The highest degree of polymer ordering combined with significant bis-fullerene phase separation and segregation of bis-fullerene to the air surface is obtained by SA in a solvent vapor that ismore » selective for the bis-fullerene. The resultant morphology increases PCE by 190%. These results indicate that solvent annealing with judicious solvent choice provides a unique tool to tune the morphology of LBP bisfullerene BHJ system, providing sufficient polymer ordering, formation of a bis-fullerene pure phase, and segregation of bis-fullerene to the air surface to optimize the morphology of the active layer. Furthermore, this process is broadly applicable to improving current disappointing LBP bis-fullerene systems to optimize their morphology and OPV performance post-deposition, including higher VOC and power conversion efficiency.« less

Authors:
 [1];  [2];  [2];  [3]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering
  3. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1159500
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of Materials Chemistry. A
Additional Journal Information:
Journal Volume: 2; Journal Issue: 25; Journal ID: ISSN 2050-7488
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Chen, Huipeng, Hsiao, Yu-Che, Hu, Bin, and Dadmun, Mark. Control of morphology and function of low band gap polymer–bis-fullerene mixed heterojunctions in organic photovoltaics with selective solvent vapor annealing. United States: N. p., 2014. Web. doi:10.1039/c4ta01436g.
Chen, Huipeng, Hsiao, Yu-Che, Hu, Bin, & Dadmun, Mark. Control of morphology and function of low band gap polymer–bis-fullerene mixed heterojunctions in organic photovoltaics with selective solvent vapor annealing. United States. doi:10.1039/c4ta01436g.
Chen, Huipeng, Hsiao, Yu-Che, Hu, Bin, and Dadmun, Mark. Wed . "Control of morphology and function of low band gap polymer–bis-fullerene mixed heterojunctions in organic photovoltaics with selective solvent vapor annealing". United States. doi:10.1039/c4ta01436g.
@article{osti_1159500,
title = {Control of morphology and function of low band gap polymer–bis-fullerene mixed heterojunctions in organic photovoltaics with selective solvent vapor annealing},
author = {Chen, Huipeng and Hsiao, Yu-Che and Hu, Bin and Dadmun, Mark},
abstractNote = {We reported how by replacing PCBM with a bis-adduct fullerene (i.e. ICBA) we significantly improve the open circuit voltage (VOC) and power conversion efficiency (PCE) in P3HT bulk heterojunctions. But, for the most promising low band-gap polymer (LBP) systems, replacing PCBM with ICBA results in very poor shortcircuit current (JSC) and PCE although the VOC is significantly improved. Therefore, in this work, we have completed small angle neutron scattering and neutron reflectometry experiments to study the impact of post-deposition solvent annealing (SA) with control of solvent quality on the morphology and performance of LBP bis-fullerene BHJ photovoltaics. Our results show that SA in a solvent that is selective for the LBP results in a depletion of bis-fullerene near the air surface, which limits device performance. SA in a solvent vapor which has similar solubility for polymer and bis-fullerene results in a higher degree of polymer ordering, bis-fullerene phase separation, and segregation of the bis-fullerene to the air surface, which facilitates charge transport and increases power conversion efficiency (PCE) by 100%. The highest degree of polymer ordering combined with significant bis-fullerene phase separation and segregation of bis-fullerene to the air surface is obtained by SA in a solvent vapor that is selective for the bis-fullerene. The resultant morphology increases PCE by 190%. These results indicate that solvent annealing with judicious solvent choice provides a unique tool to tune the morphology of LBP bisfullerene BHJ system, providing sufficient polymer ordering, formation of a bis-fullerene pure phase, and segregation of bis-fullerene to the air surface to optimize the morphology of the active layer. Furthermore, this process is broadly applicable to improving current disappointing LBP bis-fullerene systems to optimize their morphology and OPV performance post-deposition, including higher VOC and power conversion efficiency.},
doi = {10.1039/c4ta01436g},
journal = {Journal of Materials Chemistry. A},
issn = {2050-7488},
number = 25,
volume = 2,
place = {United States},
year = {2014},
month = {5}
}

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