Utilizing energy transfer in binary and ternary bulk heterojunction organic solar cells

Krishna Feron, James M. Cave, Mahir N. Thameel, Connor O'Sullivan, Renee Kroon, Mats R. Andersson, Xiaojing Zhou, Christopher J. Fell, Warwick J. Belcher, Alison B. Walker, Paul C. Dastoor

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Abstract

Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We used fluorescence and absorption spectroscopy to determine the energy disorder and Förster radii for poly(3-hexylthiophene-2,5-diyl), [6,6]-phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (DIBSq), and poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3′,2′-h][1,5]naphthyridine-5,10-dione). Heterogeneous energy transfer is found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favoring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. We explain how energy transfer can be exploited to eliminate additional energy losses in ternary bulk heterojunction solar cells, thus increasing their open-circuit voltage without loss in short-circuit current. In particular, we show that it is important that the DIBSq is located at the electron donor-acceptor interface; otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modeling shows that only small amounts of DIBSq (<5% by weight) are needed to achieve substantial performance improvementsndue to long-range energy transfer.

Original languageEnglish
Pages (from-to)20928-20937
Number of pages10
JournalACS Applied Materials and Interfaces
Volume8
Issue number32
DOIs
Publication statusPublished - 17 Aug 2016

Keywords

  • photovoltaics
  • energy level optimization
  • energy transfer
  • exciton dissociation
  • Monte Carlo
  • ternary organic solar cells

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    Feron, K., Cave, J. M., Thameel, M. N., O'Sullivan, C., Kroon, R., Andersson, M. R., Zhou, X., Fell, C. J., Belcher, W. J., Walker, A. B., & Dastoor, P. C. (2016). Utilizing energy transfer in binary and ternary bulk heterojunction organic solar cells. ACS Applied Materials and Interfaces, 8(32), 20928-20937. https://doi.org/10.1021/acsami.6b05474