Molecular engineering to improve carrier lifetimes for organic photovoltaic devices with thick active layers

Stefan D. Oosterhout*, Wade A. Braunecker, Zbyslaw R. Owczarczyk, Alexander L. Ayzner, Michael F. Toney, Dana C. Olson, Nikos Kopidakis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The morphology of the bulk heterojunction absorber layer in an organic photovoltaic (OPV) device has a profound effect on the electrical properties and efficiency of the device. Previous work has consistently demonstrated that the solubilizing side-chains of the donor material affect these properties and device performance in a non-trivial way. Here, using Time-Resolved Microwave Conductivity (TRMC), we show by direct measurements of carrier lifetimes that the choice of side chains can also make a substantial difference in photocarrier dynamics. We have previously demonstrated a correlation between peak photoconductance measured by TRMC and device efficiencies; here, we demonstrate that TRMC photocarrier dynamics have an important bearing on device performance in a case study of devices made from donor materials with linear vs. branched side-chains and with variable active layer thicknesses. We use Grazing-Incidence Wide Angle X-ray Scattering to elucidate the cause of the different carrier lifetimes as a function of different aggregation behavior in the polymers. Ultimately, the results help establish TRMC as a technique for screening OPV donor materials whose devices maintain performance in thick active layers (>250 nm) designed to improve light harvesting, film reproducibility, and ease of processing.

Original languageEnglish
Pages (from-to)57-65
Number of pages9
JournalOrganic Electronics
Volume47
DOIs
Publication statusPublished - 1 Aug 2017
Externally publishedYes

Keywords

  • time-resolved microwave conductivity
  • organic photovoltaics
  • X-ray diffraction
  • carrier lifetime
  • layer thickness

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