The influence of solid-state microstructure on the origin and yield of long-lived photogenerated charge in neat semiconducting polymers

Obadiah G. Reid, Jennifer A Nekuda Malik, Gianluca Latini, Smita Dayal, Nikos Kopidakis, Carlos Silva, Natalie Stingelin, Gary Rumbles

Research output: Contribution to journalArticle

87 Citations (Scopus)

Abstract

The influence of solid-state microstructure on the optoelectronic properties of conjugated polymers is widely recognized, but still poorly understood. Here, we show how the microstructure of conjugated polymers controls the yield and decay dynamics of long-lived photogenerated charge in neat films. Poly(3-hexylthiophene) was used as a model system. By varying the molecular weight, we drive a transition in the polymer microstructure from nonentangled, chain-extended, paraffinic-like to entangled, semicrystalline (MW = 5.5-347 kg/mol). The molecular weight range at which this transition occurs (MW = 40-50 kg/mol) can be deduced from the drastic change in elongation at break found in tensile tests. Linear absorption measurements of free-exciton bandwidth and time-resolved microwave conductivity (TRMC) measurements of transient photoconductance track the concomitant evolution in optoelectronic properties of the polymer as a function of MW. TRMC measurements show that the yield of free photogenerated charge increases with increasing molecular weight in the paraffinic regime and saturates at the transition into the entangled, semicrystalline regime. This transition in carrier yield correlates with a sharp transition in free-exciton bandwidth and decay dynamics at a similar molecular weight. We propose that the transition in microstructure controls the yield and decay dynamics of long-lived photogenerated charge. The evolution of a semicrystalline structure with well-defined interfaces between amorphous and crystalline domains of the polymer is required for spatial separation of the electron and hole. This structural characteristic not only largely controls the yield of free charges, but also serves as a recombination center, where mobile holes encounter a bath of dark electrons resident in the amorphous phase and recombine with quasi first-order kinetics.

Original languageEnglish
Pages (from-to)27-37
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume50
Issue number1
DOIs
Publication statusPublished - Jan 1 2012

Fingerprint

Semiconducting polymers
Molecular weight
solid state
Polymers
microstructure
Microstructure
molecular weight
Conjugated polymers
polymers
Excitons
Optoelectronic devices
Microwaves
Bandwidth
Electrons
decay
Electron transitions
excitons
bandwidth
microwaves
Elongation

Keywords

  • charge transport
  • conjugated polymers
  • microwave conductivity
  • molecular weight dependence
  • P3HT
  • photophysics
  • semiconducting polymers
  • solid-state structure
  • structure-property relations

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

Cite this

The influence of solid-state microstructure on the origin and yield of long-lived photogenerated charge in neat semiconducting polymers. / Reid, Obadiah G.; Malik, Jennifer A Nekuda; Latini, Gianluca; Dayal, Smita; Kopidakis, Nikos; Silva, Carlos; Stingelin, Natalie; Rumbles, Gary.

In: Journal of Polymer Science, Part B: Polymer Physics, Vol. 50, No. 1, 01.01.2012, p. 27-37.

Research output: Contribution to journalArticle

Reid, Obadiah G. ; Malik, Jennifer A Nekuda ; Latini, Gianluca ; Dayal, Smita ; Kopidakis, Nikos ; Silva, Carlos ; Stingelin, Natalie ; Rumbles, Gary. / The influence of solid-state microstructure on the origin and yield of long-lived photogenerated charge in neat semiconducting polymers. In: Journal of Polymer Science, Part B: Polymer Physics. 2012 ; Vol. 50, No. 1. pp. 27-37.
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