Effect of molecular weight on the photovoltaic performance of a low band gap copolymer blended with ICBA

Olzhas Ibraikulov, Rony Bechara, Patrick Lev́êque, Nicolas Leclerc, Galymzhan Koishiyev, Thomas Heiser

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An increase in molecular weight of the polymer generally impedes solubility in common solvents and may influence the polymer optoelectronic properties as well. Indeed, higher molecular weights are expected to increase charge carrier mobilities and therefore give rise to better photovoltaic performances of bulk heterojunction solar cells. In this work, we use copolymers based on 2,1,3-benzothiadiazole, thiophene and thieno[3,2-b]thiophene units of various fractions differing in molecular weights almost by a factor of 4 with a fullerene based acceptor material Indene-C60 Bisadduct (IC[60]BA) to elaborate bulk heterojunction solar cells. We investigate the influence of post-deposition annealing temperatures and polymer: fullerene ratios on the final cell performances. We use IC[60]BA as an acceptor to enhance the open circuit voltage due to its high lying LUMO level [1]. Additionally, charge carrier mobilities were probed using bottom contact organic field-effect transistors. As expected, higher molecular weights (as long as homogeneity was maintained) resulted in an increase of the hole field-effect mobility (up to 7x10-3 cm 2V-1s-1). Consequently, the power conversion efficiencies of bulk heterojunction solar cells could be improved by increasing the copolymer molecular weight. A power conversion efficiency of 2.4% with an open circuit voltage of 0.82V was reached in a standard device configuration with aluminum as a cathode after post-deposition thermal annealing.

Original languageEnglish
Title of host publicationOrganic and Hybrid Photovoltaic Materials and Devices
PublisherMaterials Research Society
Pages14-19
Number of pages6
ISBN (Print)9781632661265
DOIs
Publication statusPublished - Jan 1 2013
Event2013 MRS Spring Meeting - San Francisco, CA, United States
Duration: Apr 1 2013Apr 5 2013

Publication series

NameMaterials Research Society Symposium Proceedings
Volume1537
ISSN (Print)0272-9172

Other

Other2013 MRS Spring Meeting
CountryUnited States
CitySan Francisco, CA
Period4/1/134/5/13

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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    Ibraikulov, O., Bechara, R., Lev́êque, P., Leclerc, N., Koishiyev, G., & Heiser, T. (2013). Effect of molecular weight on the photovoltaic performance of a low band gap copolymer blended with ICBA. In Organic and Hybrid Photovoltaic Materials and Devices (pp. 14-19). (Materials Research Society Symposium Proceedings; Vol. 1537). Materials Research Society. https://doi.org/10.1557/opl.2013.705