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Title: Insights into the Morphological Instability of Bulk Heterojunction PTB7-Th/PCBM Solar Cells upon High-Temperature Aging

Abstract

The impact of the morphological stability of the donor/acceptor mixture under thermal stress on the photovoltaic properties of bulk heterojunction (BHJ) solar cells based on the poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']-di-thiophene-2,6-diyl-alt-(4-(2 ethylhexyl)-3-fluorothieno[3,4-b]-thiophene)-2-carboxylate-2,6-diyl]/phenyl-C61-butyric acid methylester (PTB7-Th/PC61BM) blend is extensively investigated. Both optical microscopy and transmission electron microscopy micrographs show that long-term high-temperature aging stimulates the formation of microscale clusters, the size of which, however, is about 1 order of magnitude smaller than those observed in thermally annealed poly(3hexylthiophene)/PC61BM composite film. The multilength-scale evolution of the morphology of PTB7-Th/PC61BM film from the scattering profiles of grazing incidence small-angle and wide-angle X-ray scattering indicates the PC61BM molecules spatially confine the self-organization of polymer chains into large domains during cast drying and upon thermal activation. Moreover, some PC61BM molecules accumulate into ~30-40 nm clusters, the number of which increases with heating time. Therefore, the hole mobility in the active layer decays much more rapidly than the electron mobility, leading to unbalanced charge transport and degraded cell performance. Importantly, the three-component blend that is formed by replacing a small amount of PC61BM in the active layer with the bis-adduct of PC61BM (bis-P61M) exhibits robust morphology against thermal stress. Accordingly, the PTB7-Th/PC61BM:bis-PC61BM (8 wt %) device has an extremely stablemore » power conversion efficiency.« less

Authors:
; ; ; ; ; ; ORCiD logo
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:
1392506
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Applied Materials and Interfaces; Journal Volume: 9; Journal Issue: 17
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Hsieh, Yen-Ju, Huang, Yu-Ching, Liu, Wei-Shin, Su, Yu-An, Tsao, Cheng-Si, Rwei, Syang-Peng, and Wang, Leeyih. Insights into the Morphological Instability of Bulk Heterojunction PTB7-Th/PCBM Solar Cells upon High-Temperature Aging. United States: N. p., 2017. Web. doi:10.1021/acsami.7b01296.
Hsieh, Yen-Ju, Huang, Yu-Ching, Liu, Wei-Shin, Su, Yu-An, Tsao, Cheng-Si, Rwei, Syang-Peng, & Wang, Leeyih. Insights into the Morphological Instability of Bulk Heterojunction PTB7-Th/PCBM Solar Cells upon High-Temperature Aging. United States. doi:10.1021/acsami.7b01296.
Hsieh, Yen-Ju, Huang, Yu-Ching, Liu, Wei-Shin, Su, Yu-An, Tsao, Cheng-Si, Rwei, Syang-Peng, and Wang, Leeyih. Tue . "Insights into the Morphological Instability of Bulk Heterojunction PTB7-Th/PCBM Solar Cells upon High-Temperature Aging". United States. doi:10.1021/acsami.7b01296.
@article{osti_1392506,
title = {Insights into the Morphological Instability of Bulk Heterojunction PTB7-Th/PCBM Solar Cells upon High-Temperature Aging},
author = {Hsieh, Yen-Ju and Huang, Yu-Ching and Liu, Wei-Shin and Su, Yu-An and Tsao, Cheng-Si and Rwei, Syang-Peng and Wang, Leeyih},
abstractNote = {The impact of the morphological stability of the donor/acceptor mixture under thermal stress on the photovoltaic properties of bulk heterojunction (BHJ) solar cells based on the poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']-di-thiophene-2,6-diyl-alt-(4-(2 ethylhexyl)-3-fluorothieno[3,4-b]-thiophene)-2-carboxylate-2,6-diyl]/phenyl-C61-butyric acid methylester (PTB7-Th/PC61BM) blend is extensively investigated. Both optical microscopy and transmission electron microscopy micrographs show that long-term high-temperature aging stimulates the formation of microscale clusters, the size of which, however, is about 1 order of magnitude smaller than those observed in thermally annealed poly(3hexylthiophene)/PC61BM composite film. The multilength-scale evolution of the morphology of PTB7-Th/PC61BM film from the scattering profiles of grazing incidence small-angle and wide-angle X-ray scattering indicates the PC61BM molecules spatially confine the self-organization of polymer chains into large domains during cast drying and upon thermal activation. Moreover, some PC61BM molecules accumulate into ~30-40 nm clusters, the number of which increases with heating time. Therefore, the hole mobility in the active layer decays much more rapidly than the electron mobility, leading to unbalanced charge transport and degraded cell performance. Importantly, the three-component blend that is formed by replacing a small amount of PC61BM in the active layer with the bis-adduct of PC61BM (bis-P61M) exhibits robust morphology against thermal stress. Accordingly, the PTB7-Th/PC61BM:bis-PC61BM (8 wt %) device has an extremely stable power conversion efficiency.},
doi = {10.1021/acsami.7b01296},
journal = {ACS Applied Materials and Interfaces},
number = 17,
volume = 9,
place = {United States},
year = {Tue Apr 18 00:00:00 EDT 2017},
month = {Tue Apr 18 00:00:00 EDT 2017}
}