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Title: Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size

Abstract

High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100’s of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu 3N@PC 80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu 3N@PC 80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu 3N@PC 80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu 3N@PC 80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.

Authors:
 [1];  [2];  [3];  [4];  [2];  [4];  [2];  [3]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Material Science Division
  2. Univ. Erlangen-Nurnberg, Erlangen (Germany). Inst. Materials for Electronics and Energy Technology (i-MEET)
  3. Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Material Science
  4. Univ. Erlangen-Nurnberg, Erlangen (Germany)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
National Science Foundation (NSF); German Research Foundation (DFG); USDOE
OSTI Identifier:
1418486
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 6; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Roehling, John D., Baran, Derya, Sit, Joseph, Kassar, Thaer, Ameri, Tayebeh, Unruh, Tobias, Brabec, Christoph J., and Moule, Adam J.. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size. United States: N. p., 2016. Web. doi:10.1038/srep30915.
Roehling, John D., Baran, Derya, Sit, Joseph, Kassar, Thaer, Ameri, Tayebeh, Unruh, Tobias, Brabec, Christoph J., & Moule, Adam J.. Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size. United States. doi:10.1038/srep30915.
Roehling, John D., Baran, Derya, Sit, Joseph, Kassar, Thaer, Ameri, Tayebeh, Unruh, Tobias, Brabec, Christoph J., and Moule, Adam J.. Mon . "Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size". United States. doi:10.1038/srep30915. https://www.osti.gov/servlets/purl/1418486.
@article{osti_1418486,
title = {Nanoscale Morphology of PTB7 Based Organic Photovoltaics as a Function of Fullerene Size},
author = {Roehling, John D. and Baran, Derya and Sit, Joseph and Kassar, Thaer and Ameri, Tayebeh and Unruh, Tobias and Brabec, Christoph J. and Moule, Adam J.},
abstractNote = {High efficiency polymer:fullerene photovoltaic device layers self-assemble with hierarchical features from ångströms to 100’s of nanometers. The feature size, shape, composition, orientation, and order all contribute to device efficiency and are simultaneously difficult to study due to poor contrast between carbon based materials. This study seeks to increase device efficiency and simplify morphology measurements by replacing the typical fullerene acceptor with endohedral fullerene Lu3N@PC80BEH. The metal atoms give excellent scattering contrast for electron beam and x-ray experiments. Additionally, Lu3N@PC80BEH has a lower electron affinity than standard fullerenes, which can raise the open circuit voltage of photovoltaic devices. Electron microscopy techniques are used to produce a detailed account of morphology evolution in mixtures of Lu3N@PC80BEH with the record breaking donor polymer, PTB7 and coated using solvent mixtures. We demonstrate that common solvent additives like 1,8-diiodooctane or chloronapthalene do not improve the morphology of endohedral fullerene devices as expected. The poor device performance is attributed to the lack of mutual miscibility between this particular polymer:fullerene combination and to co-crystallization of Lu3N@PC80BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.},
doi = {10.1038/srep30915},
journal = {Scientific Reports},
number = 1,
volume = 6,
place = {United States},
year = {Mon Aug 08 00:00:00 EDT 2016},
month = {Mon Aug 08 00:00:00 EDT 2016}
}

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