Open AccessMolecular weight dependence of carrier mobility and recombination rate in neat P3HT films
Author(s) -
Dixon Alex G.,
Visvanathan Rayshan,
Clark Noel A.,
Stingelin Natalie,
Kopidakis Nikos,
Shaheen Sean E.
Publication year - 2018
Publication title -
journal of polymer science part b: polymer physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.65
H-Index - 145
eISSN - 1099-0488
pISSN - 0887-6266
DOI - 10.1002/polb.24531
Subject(s) - crystallinity , amorphous solid , crystallite , materials science , microstructure , polymer , phase (matter) , charge carrier , electron mobility , recombination , polymer chemistry , chemical physics , crystallography , chemistry , composite material , organic chemistry , optoelectronics , metallurgy , gene , biochemistry
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, M w , 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 M w = 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 M w , which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56 , 31–35