Signatures of intracrystallite and intercrystallite limitations of charge transport in polythiophenes

Published

September 20, 2016

Author(s)

Kiarash Vakhshouri, Brandon Smith, Edwin Chan, Chenchen Wang, Alberto Salleo, Cheng Wang, Alexander Hexemer, Enrique Gomez

Abstract

Charge carrier mobilities in conjugated semicrystalline polymers depend on morphological parameters such as crystallinity, crystal orientation, and connectivity between ordered regions. Despite recent progress in the development of conducting polymers, the complex interplay between the aforementioned parameters and their impact on charge transport is not fully understood. By varying the casting solvents and thermal annealing, we have systematically modulated the crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[2,5-bis(3- hexadecylthiophen-2-yl)thieno(3,2-b)thiophene] (PBTTT) thin films to examine the role of microstructure on charge mobilities. In particular, we achieve equal crystallinities through 1 different processing routes to examine the role of structural parameters beyond the crystallinity on charge mobilities. As expected, a universal relationship does not exist between the crystallinity in both P3HT and PBTTT active layers and the charge mobility in devices. In P3HT films, higher boiling point solvents yield longer conjugation lengths, an indicator of stronger intracrystalline order, and therefore higher device mobilities. In contrast, the charge mobilities of PBTTT devices depend on the interconnectivity between crystallites in the active layer and intercrystalline order.

Citation

Macromolecules

Pub Type

Journals

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Keywords

PBTTT, P3HT, polymer thin films, OPV

Citation

Vakhshouri, K. , Smith, B. , Chan, E. , Wang, C. , Salleo, A. , Wang, C. , Hexemer, A. and Gomez, E. (2016), Signatures of intracrystallite and intercrystallite limitations of charge transport in polythiophenes, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920744 (Accessed March 13, 2025)