Exploring the Photophysics of N-Type Polymer N2200

Research output: NRELPoster

Abstract

The polymer interphase is a complex environment comprised of polymer chains, solvent molecules, and electrolyte ions. However, the microenvironments that these ingredients produce is both poorly-understood and difficult to investigate given the system's inherent structural heterogeneity. Nonetheless, a fundamental understanding of the structure, electrochemical behavior, and excited-state dynamics is a key prerequisite to optimizing devices based on such a system - for instance, photoelectrochemical cells for the direct, light-driven production of solar hydrogen, which may minimize efficiency losses compared to sequential light harvesting and electrochemical hydrogen production in separate but linked devices. This work combines transient absorption (TA) spectroscopy, which is a powerful tool for the observation of a variety of excited states on a femto- to microsecond timescale, with time-resolved microwave conductivity (TRMC) spectroscopy, which selectively probes the dynamics of free charge carriers (FC), of a blend of a donor polymer (PTB7-Th) and acceptor polymer (N2200) in a bulk heterojunction. Initial results indicate an extension of FC lifetime and homogenization of the microenvironment on a whole-film level, not just at the surface of the polymer; however, many questions are still under active investigation, including the changes in energy of the involved polaron states, effective conjugation length, FC mobility and migration distance, etc. Additional experiments regarding the photoinitiated behavior of the blend in different environments and on different timescales are ongoing.
Original languageAmerican English
PublisherNational Renewable Energy Laboratory (NREL)
StatePublished - 2024

Publication series

NamePresented at the Electronic Processes in Organic Materials Gordon Research Conference, 7-12 July 2024, Lucca, Italy

NREL Publication Number

  • NREL/PO-5900-90467

Keywords

  • charge recombination
  • charge separation
  • electrolyte
  • HER
  • hydrogen evolution reaction
  • interphase
  • polymer
  • transient absorption

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