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

John D. Roehling; Derya Baran; Joseph Sit; Thaer Kassar; Tayebeh Ameri; Tobias Unruh; Christoph J. Brabec; Adam J. Moulé

doi:10.1038/srep30915

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

John D. Roehling, Derya Baran, Joseph Sit, Thaer Kassar, Tayebeh Ameri, Tobias Unruh, Christoph J. Brabec, Adam J. Moulé^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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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 Lu₃N@PC₈₀ BEH. The metal atoms give excellent scattering contrast for electron beam and X-ray experiments. Additionally, Lu₃N@PC₈₀ BEH 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 3 N@PC 80 BEH 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 3 N@PC 80 BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.

Original language	English (US)
Article number	30915
Journal	Scientific Reports
Volume	6
DOIs	https://doi.org/10.1038/srep30915
State	Published - Aug 8 2016
Externally published	Yes

Bibliographical note

Funding Information:
This research project was supported by the U.S. National Science Foundation under Award No. 1436273. TU and TK greatly acknowledge the Deutsche Forschungsgemeinschaft (Cluster of Excellence: Engineering of Advanced Materials) for financial support. TA and CB acknowledge the financial support of Solar Technologies go Hybrid (SolTech) and SFB 953 (Synthetic Carbon Allotropes). JDR thanks the U.S. Department of Energy (DOE) at Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 for salary support.

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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 {\aa}ngstr{\"o}ms 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@PC80 BEH. The metal atoms give excellent scattering contrast for electron beam and X-ray experiments. Additionally, Lu3N@PC80 BEH 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 3 N@PC 80 BEH 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 3 N@PC 80 BEH with 1,8-diiodooctane. This negative result explains why solvent additives mixtures are not necessarily a morphology cure-all.",

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note = "Funding Information: This research project was supported by the U.S. National Science Foundation under Award No. 1436273. TU and TK greatly acknowledge the Deutsche Forschungsgemeinschaft (Cluster of Excellence: Engineering of Advanced Materials) for financial support. TA and CB acknowledge the financial support of Solar Technologies go Hybrid (SolTech) and SFB 953 (Synthetic Carbon Allotropes). JDR thanks the U.S. Department of Energy (DOE) at Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 for salary support.",

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AU - Moulé, Adam J.

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

Abstract

Bibliographical note

ASJC Scopus subject areas

UN SDGs

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