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Title: Understanding How Processing Additives Tune the Nanoscale Morphology of High Efficiency Organic Photovoltaic Blends: From Casting Solution to Spun-Cast Thin Film

Abstract

Adding a small amount of a processing additive to the casting solution of photoactive organic blends has been demonstrated to be an effective method for achieving improved power conversion efficiency (PCE) in organic photovoltaics (OPVs). However, an understanding of the nano-structural evolution occurring in the transformation from casting solution to thin photoactive films is still lacking. In this report, the effects of the processing additive diiodooctane (DIO) on the morphology of the established blend of PBDTTT-C-T polymer and the fullerene derivative PC71BM used for OPVs are investigated, starting in the casting solution and tracing the effects in spun-cast thin films by using neutron/X-ray scattering, neutron reflectometry, and other characterization techniques. The results reveal that DIO has no observable effect on the structures of PBDTTT-C-T and PC71BM in solution; however, in the spun-cast films, it significantly promotes their molecular ordering and phase segregation, resulting in improved PCE. Thermodynamic analysis based on Flory-Huggins theory provides a rationale for the effects of DIO on different characteristics of phase segregation due to changes in concentration resulting from evaporation of the solvent and additive during film formation. Such information may help improve the rational design of ternary blends to more consistently achieve improved PCE formore » OPVs.« less

Authors:
 [1];  [2];  [3];  [1];  [4];  [5];  [6];  [7];  [4];  [4];  [1];  [1];  [3];  [1]
  1. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
  2. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Neutron Scattering Science Divisions, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
  3. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
  4. Neutron Scattering Science Divisions, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
  5. Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville TN 37996 USA
  6. Material Sciences Division, Argonne National Laboratory, Argonne Illinois 60439 USA
  7. Institute of Chemistry, Chinese Academy of Sciences, Beijing 10080 China
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division
OSTI Identifier:
1392080
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Advanced Functional Materials; Journal Volume: 24; Journal Issue: 42
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Shao, Ming, Keum, Jong Kahk, Kumar, Rajeev, Chen, Jihua, Browning, James F., Das, Sanjib, Chen, Wei, Hou, Jianhui, Do, Changwoo, Littrell, Kenneth C., Rondinone, Adam, Geohegan, David B., Sumpter, Bobby G., and Xiao, Kai. Understanding How Processing Additives Tune the Nanoscale Morphology of High Efficiency Organic Photovoltaic Blends: From Casting Solution to Spun-Cast Thin Film. United States: N. p., 2014. Web. doi:10.1002/adfm.201401547.
Shao, Ming, Keum, Jong Kahk, Kumar, Rajeev, Chen, Jihua, Browning, James F., Das, Sanjib, Chen, Wei, Hou, Jianhui, Do, Changwoo, Littrell, Kenneth C., Rondinone, Adam, Geohegan, David B., Sumpter, Bobby G., & Xiao, Kai. Understanding How Processing Additives Tune the Nanoscale Morphology of High Efficiency Organic Photovoltaic Blends: From Casting Solution to Spun-Cast Thin Film. United States. doi:10.1002/adfm.201401547.
Shao, Ming, Keum, Jong Kahk, Kumar, Rajeev, Chen, Jihua, Browning, James F., Das, Sanjib, Chen, Wei, Hou, Jianhui, Do, Changwoo, Littrell, Kenneth C., Rondinone, Adam, Geohegan, David B., Sumpter, Bobby G., and Xiao, Kai. Tue . "Understanding How Processing Additives Tune the Nanoscale Morphology of High Efficiency Organic Photovoltaic Blends: From Casting Solution to Spun-Cast Thin Film". United States. doi:10.1002/adfm.201401547.
@article{osti_1392080,
title = {Understanding How Processing Additives Tune the Nanoscale Morphology of High Efficiency Organic Photovoltaic Blends: From Casting Solution to Spun-Cast Thin Film},
author = {Shao, Ming and Keum, Jong Kahk and Kumar, Rajeev and Chen, Jihua and Browning, James F. and Das, Sanjib and Chen, Wei and Hou, Jianhui and Do, Changwoo and Littrell, Kenneth C. and Rondinone, Adam and Geohegan, David B. and Sumpter, Bobby G. and Xiao, Kai},
abstractNote = {Adding a small amount of a processing additive to the casting solution of photoactive organic blends has been demonstrated to be an effective method for achieving improved power conversion efficiency (PCE) in organic photovoltaics (OPVs). However, an understanding of the nano-structural evolution occurring in the transformation from casting solution to thin photoactive films is still lacking. In this report, the effects of the processing additive diiodooctane (DIO) on the morphology of the established blend of PBDTTT-C-T polymer and the fullerene derivative PC71BM used for OPVs are investigated, starting in the casting solution and tracing the effects in spun-cast thin films by using neutron/X-ray scattering, neutron reflectometry, and other characterization techniques. The results reveal that DIO has no observable effect on the structures of PBDTTT-C-T and PC71BM in solution; however, in the spun-cast films, it significantly promotes their molecular ordering and phase segregation, resulting in improved PCE. Thermodynamic analysis based on Flory-Huggins theory provides a rationale for the effects of DIO on different characteristics of phase segregation due to changes in concentration resulting from evaporation of the solvent and additive during film formation. Such information may help improve the rational design of ternary blends to more consistently achieve improved PCE for OPVs.},
doi = {10.1002/adfm.201401547},
journal = {Advanced Functional Materials},
number = 42,
volume = 24,
place = {United States},
year = {Tue Aug 26 00:00:00 EDT 2014},
month = {Tue Aug 26 00:00:00 EDT 2014}
}