Molecular Weight Dependence of Carrier Mobility and Recombination Rate in Neat P3HT Films

Nikos Kopidakis, Alex Dixon, Rayshan Visvanathan, Noel Clark, Natalie Stingelin, Sean Shaheen

Research output: Contribution to journalArticlepeer-review

41 Scopus Citations

Abstract

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3-hexylthyophene (P3HT) were determined for a range of materials of weight-average molecular weights, Mw, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one-phase, paraffinic-like structure comprised of chain-extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of Mw = 48 kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two-phase structure with increasing Mw, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination.

Original languageAmerican English
Pages (from-to)31-35
Number of pages5
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume56
Issue number1
DOIs
StatePublished - 2018

Bibliographical note

Publisher Copyright:
© 2017 Wiley Periodicals, Inc.

NREL Publication Number

  • NREL/JA-5900-70633

Keywords

  • carrier mobility
  • carrier recombination
  • CELIV
  • conjugated polymer
  • molecular weight
  • P3HT

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