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Title: Understanding how processing additives tune 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 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, we investigate the effects of the processing additive diiodooctane (DIO) on the morphology of OPV blend of PBDTTT-C-T and fullerene derivative, PC71BM in a casting solution and in spun-cast thin films by using neutron/x-ray scattering, neutron reflectometry and other characterization techniques. The results reveal that DIO has no effect on the solution structures of PBDTTT-C-T and PC71BM. In the spun-cast films, however, DIO is found to promote significantly the molecular ordering of PBDTTT-C-T and PC71BM, and phase segregation, resulting in the improved PCE. Thermodynamic analysis based on Flory-Huggins theory provides a rationale for the effects of DIO on different characteristics of phase segregation as a solvent and due to evaporationg during the film formation. Such information may enable improved rational design of ternary blends to more consistently achieve improved PCE for OPVs.

Authors:
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [1];  [1];  [4];  [1];  [1];  [1];  [1]
  1. ORNL
  2. Argonne National Laboratory (ANL)
  3. Chinese Academy of Sciences (CAS), Institute of Chemistry
  4. University of Tennessee, Knoxville (UTK)
Publication Date:
Research Org.:
Center for Nanophase Materials Sciences (CNMS); 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:
1154828
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Advanced Functional Materials
Additional Journal Information:
Journal Name: Advanced Functional Materials
Country of Publication:
United States
Language:
English

Citation Formats

Shao, Ming, Keum, Jong Kahk, Kumar, Rajeev, Chen, Jihua, Browning, Jim, Chen, Wei, Jianhui, Hou, Do, Changwoo, Littrell, Ken, Sanjib, Das, Rondinone, Adam Justin, Geohegan, David B, Sumpter, Bobby G, and Xiao, Kai. Understanding how processing additives tune 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, Jim, Chen, Wei, Jianhui, Hou, Do, Changwoo, Littrell, Ken, Sanjib, Das, Rondinone, Adam Justin, Geohegan, David B, Sumpter, Bobby G, & Xiao, Kai. Understanding how processing additives tune 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, Jim, Chen, Wei, Jianhui, Hou, Do, Changwoo, Littrell, Ken, Sanjib, Das, Rondinone, Adam Justin, Geohegan, David B, Sumpter, Bobby G, and Xiao, Kai. Wed . "Understanding how processing additives tune 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_1154828,
title = {Understanding how processing additives tune 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, Jim and Chen, Wei and Jianhui, Hou and Do, Changwoo and Littrell, Ken and Sanjib, Das and Rondinone, Adam Justin 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 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, we investigate the effects of the processing additive diiodooctane (DIO) on the morphology of OPV blend of PBDTTT-C-T and fullerene derivative, PC71BM in a casting solution and in spun-cast thin films by using neutron/x-ray scattering, neutron reflectometry and other characterization techniques. The results reveal that DIO has no effect on the solution structures of PBDTTT-C-T and PC71BM. In the spun-cast films, however, DIO is found to promote significantly the molecular ordering of PBDTTT-C-T and PC71BM, and phase segregation, resulting in the improved PCE. Thermodynamic analysis based on Flory-Huggins theory provides a rationale for the effects of DIO on different characteristics of phase segregation as a solvent and due to evaporationg during the film formation. Such information may enable improved rational design of ternary blends to more consistently achieve improved PCE for OPVs.},
doi = {10.1002/adfm.201401547},
journal = {Advanced Functional Materials},
number = ,
volume = ,
place = {United States},
year = {2014},
month = {1}
}