Photovoltaic Blend Microstructure for High Efficiency Post-Fullerene Solar Cells. To Tilt or Not To Tilt?

Published

August 5, 2019

Author(s)

Subhrangsu Mukherjee, Dean M. DeLongchamp, Gang Wang, Steven M. Swick, Micaela Matta, Joseph Strzalka, Thomas Aldrich, Ferdinand Melkonyan, Antonio Facchetti, Tobin Marks, Jenna L. Logsdon, Simone Fabiano, Wei Huang, Tony Yang, Amod Timalsina, Natalia Powers-Riggs, Joaquin Alzola, Ryan M. Young, Michael R. Wasielewski, George C. Schatz

Abstract

Achieving efficient polymer solar cells (PSCs) requires a structurally optimal donor–acceptor heterojunction morphology. Here we report the combined experimental and theoretical characterization of a benzodithiophene–benzothiadiazole donor polymer series (PBTZF4-R; R = alkyl substituent) blended with the non-fullerene acceptor ITIC-Th and analyze the effects of substituent dimensions on blend morphology, charge transport, carrier dynamics, and PSC metrics. Varying substituent dimensions has a pronounced effect on the blend morphology with a direct link between domain purity, to some extent domain dimensions, and charge generation and collection. The polymer with the smallest alkyl substituent yields the highest PSC power conversion efficiency (PCE, 11%), reflecting relatively small, high-purity domains and possibly benefiting from “matched” donor polymer–small molecule acceptor orientations. The distinctive morphologies arising from the substituents are investigated using molecular dynamics (MD) simulations which reveal that substituent dimensions dictate a well-defined set of polymer conformations, in turn driving chain aggregation and, ultimately, the various film morphologies and mixing with acceptor small molecules. A straightforward energetic parameter explains the experimental polymer domain morphological trends, hence PCE, and suggests strategies for substituent selection to optimize PSC materials morphologies.

Citation

Journal of the American Chemical Society

Pub Type

Journals

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https://doi.org/10.1021/jacs.9b03770

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Citation

Mukherjee, S. , DeLongchamp, D. , Wang, G. , Swick, S. , Matta, M. , Strzalka, J. , Aldrich, T. , Melkonyan, F. , Facchetti, A. , Marks, T. , Logsdon, J. , Fabiano, S. , Huang, W. , Yang, T. , Timalsina, A. , Powers-Riggs, N. , Alzola, J. , Young, R. , Wasielewski, M. and Schatz, G. (2019), Photovoltaic Blend Microstructure for High Efficiency Post-Fullerene Solar Cells. To Tilt or Not To Tilt?, Journal of the American Chemical Society, [online], https://doi.org/10.1021/jacs.9b03770 (Accessed May 10, 2024)