Understanding Solidification of Polythiophene Thin Films during Spin-Coating: Effects of Spin-Coating Time and Processing Additives

Abstract

Spin-coating has been used extensively in the fabrication of electronic devices; however, the effects of the processing parameters have not been fully explored. Here, we systematically characterize the effects of the spin-coating time on the microstructure evolution during semiconducting polymer solidification in an effort to establish the relationship between this parameter and the performances of the resulting polymer field-effect transistors (FETs). We found that a short spin-coating time of a few seconds dramatically improve the morphology and molecular order in a conjugated polymer thin film because the π-π stacking structures formed by the polymer molecules grow slowly and with a greater degree of order due to the residual solvent present in the wet film. The improved ordering is correlated with improved charge carrier transport in the FETs prepared from these films. We also demonstrated the effects of various processing additives on the resulting FET characteristics as well as on the film drying behavior during spin-coating. The physical properties of the additives are found to affect the film drying process and the resulting device performance.

IR spectroscopic and photoluminescence studies of plasma polymerized organic thin films based on tea tree oil

“…This film also shows broad weak absorption bands at 558 nm (Fig. 3a) contributed to interchain π-π stacking interactions of rings similar to that reported in polythiophene films prepared by spin coating method [31].…”

Comparing electron- and hole transporting semiconductors in ion sensitive water- gated transistors

“…The hole transporting semiconducting polymer regioregular poly(3-hexyl)thiophene (rrP3HT) was purchased from Aldrich (Cat No 698989, electronic grade 99.995% trace metal basis), dissolved at 4 mg/mL in toluene solution, heated gently at 75 °C for ≈ 10 min, and spin cast onto contact substrates at 2000 rpm for 60 s. After casting, films were dried under dynamic vacuum at 120 °C for 1 h. The semicrystalline morphology of rrP3HT films used in sensors has been studied in detail before, e.g. [27][28][29]. Zinc oxide films were prepared by spraying 3 'puffs' of 100 mM ZnCl 2 solution in DI water onto similar TFT substrates heated to 400 °C o on a hotplate, which leads to the formation of semiconducting ZnO films('spray pyrolysis', more processing details in [30]).…”

Influence of Active Layer Processing on Electrical Properties and Efficiency of Polymer-Fullerene Organic Solar Cells

“…Organic photovoltaic cells with a polymer:fullerene bulk heterojunction active layer are inexpensive sources of renewable energy, having maximum reported efficiency of about 11% [1]. The most popular acceptor materials are fullerene derivatives, while there is a broad range of proposed donor materials ranging from the most popular polythiophenes [2][3][4][5][6][7][8] to less popular but promising polyazomethines [9,10]. The main research on improvement of polymer: fullerene cell efficiency is focused on two approaches: (i) searching for better polymer that would have a smaller energy gap, more suitable highly occupied molecular orbital (HOMO) and lowly unoccupied molecular orbital (LUMO) energy levels regarding the acceptor respective ones, and increased carrier mobilities; (ii) improvement of crystal structure in order to obtain better electrical parameters (higher conductivity, lower leakage).…”