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Title: Visualization of Hierarchical Nanodomains in Polymer/Fullerene Bulk Heterojunction Solar Cells

Abstract

Here, traditional electron microscopy techniques such as bright-field imaging provide poor contrast for organic films and identification of structures in amorphous material can be problematic, particularly in high-performance organic solar cells. By combining energy-filtered corrected transmission electron microscopy, together with electron energy loss and X-ray energy-dispersive hyperspectral imaging, we have imaged PTB7/ PC 61BM blended polymer optical photovoltaic films, and were able to identify domains ranging in size from several hundred nanometers to several nanometers in extent. This work verifies that microstructural domains exist in bulk heterojunctions in PTB7/PC 61BM polymeric solar cells at multiple length scales and expands our understanding of optimal device performance providing insight for the design of even higher performance cells.

Authors:
 [1];  [1];  [2];  [3];  [3];  [2];  [1]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States); The Univ. of Chicago, Chicago, IL (United States)
  3. The Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1239951
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Microscopy and Microanalysis
Additional Journal Information:
Journal Volume: 20; Journal Issue: 05; Journal ID: ISSN 1431-9276
Publisher:
Microscopy Society of America (MSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 14 SOLAR ENERGY; X-ray energy-dispersive spectroscopy; chromatic aberration correction; electron energy-loss spectroscopy; energy-filtered transmission electron microscopy; organic photovoltaics

Citation Formats

Wen, Jianguo, Miller, Dean J., Chen, Wei, Xu, Tao, Yu, Luping, Darling, Seth B., and Zaluzec, Nestor J. Visualization of Hierarchical Nanodomains in Polymer/Fullerene Bulk Heterojunction Solar Cells. United States: N. p., 2014. Web. doi:10.1017/S1431927614001615.
Wen, Jianguo, Miller, Dean J., Chen, Wei, Xu, Tao, Yu, Luping, Darling, Seth B., & Zaluzec, Nestor J. Visualization of Hierarchical Nanodomains in Polymer/Fullerene Bulk Heterojunction Solar Cells. United States. doi:10.1017/S1431927614001615.
Wen, Jianguo, Miller, Dean J., Chen, Wei, Xu, Tao, Yu, Luping, Darling, Seth B., and Zaluzec, Nestor J. Fri . "Visualization of Hierarchical Nanodomains in Polymer/Fullerene Bulk Heterojunction Solar Cells". United States. doi:10.1017/S1431927614001615. https://www.osti.gov/servlets/purl/1239951.
@article{osti_1239951,
title = {Visualization of Hierarchical Nanodomains in Polymer/Fullerene Bulk Heterojunction Solar Cells},
author = {Wen, Jianguo and Miller, Dean J. and Chen, Wei and Xu, Tao and Yu, Luping and Darling, Seth B. and Zaluzec, Nestor J.},
abstractNote = {Here, traditional electron microscopy techniques such as bright-field imaging provide poor contrast for organic films and identification of structures in amorphous material can be problematic, particularly in high-performance organic solar cells. By combining energy-filtered corrected transmission electron microscopy, together with electron energy loss and X-ray energy-dispersive hyperspectral imaging, we have imaged PTB7/ PC61BM blended polymer optical photovoltaic films, and were able to identify domains ranging in size from several hundred nanometers to several nanometers in extent. This work verifies that microstructural domains exist in bulk heterojunctions in PTB7/PC61BM polymeric solar cells at multiple length scales and expands our understanding of optimal device performance providing insight for the design of even higher performance cells.},
doi = {10.1017/S1431927614001615},
journal = {Microscopy and Microanalysis},
number = 05,
volume = 20,
place = {United States},
year = {Fri Jun 20 00:00:00 EDT 2014},
month = {Fri Jun 20 00:00:00 EDT 2014}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 6works
Citation information provided by
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  • PTB7 semiconducting copolymer comprising thieno[3,4-b]thiophene and benzodithiophene alternating repeat units set a historic record of solar energy conversion efficiency (7.4%) in polymer/fullerene bulk heterojunction solar cells. To further improve solar cell performance, a thorough understanding of structure-property relationships associated with PTB7/fullerene and related organic photovoltaic (OPV) devices is crucial. Traditionally, OPV active layers are viewed as an interpenetrating network of pure polymers and fullerenes with discrete interfaces. Here we show that the active layer of PTB7/fullerene OPV devices in fact involves hierarchical nanomorphologies ranging from several nanometers of crystallites to tens of nanometers of nanocrystallite aggregates in PTB7-rich and fullerene-richmore » domains, themselves hundreds of nanometers in size. These hierarchical nanomorphologies are coupled to significantly enhanced exciton dissociation, which consequently contribute to photocurrent, indicating that the nanostructural characteristics at multiple length scales is one of the key factors determining the performance of PTB7 copolymer, and likely most polymer/fullerene systems, in OPV devices.« less
  • We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells.
  • High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen chargemore » trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an {approx}4 nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface.« less