Menü

Publikationsliste

Authors Janus, K. ; Chlebosz, D. ; Janke, A. ; Goldeman, W. ; Kiersnowski, A.
Title Contributions of polymer chain length, aggregation and crystallinity degrees in a model of charge carrier transport in ultrathin polymer films
Date 27.01.2023
Number 61502
Abstract Herein we report a systematic study on the quantitative relationships between molecular structure, crystallinity, aggregation, and charge carrier transport in films of poly(3-hexylthiophene-co-thiophenes) (P3HTTs) with thickness ranging from 5.7 to 8.0 nm. The P3HTTs contained 10, 20, or 30 mol % of thiophene monomer units. Our UV–Vis, X-ray diffraction, and atomic force microscopy (AFM) studies indicated that the variable thiophene content in the P3HTTs as well as the solution aging prior to film casting permitted a control over aggregation density (Xa), crystallinity degree (Xc), crystal fragmentation, and overall film morphology. Increasing the thiophene content in P3HTT caused a linear increase in the Xa and a linear drop in the Xc as well as crystal sizes. Aging the solution prior to casting resulted in a change of film morphology from granular to fibrillar and a noticeable increase in both Xa and Xc. The hole mobility determined from field-effect transistor characteristics grew nonlinearly with increasing thiophene content in P3HTT and was boosted by the aggregation-induced increase in Xa or Xc. For the 7.5 nm-thin P3HTT film (30 mol % of thiophene), the µh was as high as 0.017 cm2 × V–1 × s–1. In order to explain the observed µh variation, we have employed a model of charge transport through a series circuit, where crystals, aggregates, and the amorphous phase were considered units with different resistance to charge carrier transport. A systematic analysis of the experimental dataset revealed a quantitative correlation of the µh with the polymer end-to-end distance, interaggregate distance, and crystallinity index. Also, the correlation expressed with a single equation derived in this work enabled estimation of the minimum mobility of the amorphous phase and maximum mobility of the crystal phase in the quasi-two-dimensional films. Our original findings suggest that in quantitative considerations of charge transport in the ultrathin polymer films, the morphology should be considered secondary to molar mass and phase composition.
Publisher Macromolecules
Wikidata
Citation Macromolecules 56 (2023) 964-973
DOI https://doi.org/10.1021/ACS.MACROMOL.2C01998
Tags

Back to list