Poly(2-alkyl-2-oxazoline) electrode interlayers for improved n-type organic field effect transistor performance

Thin film interlayer materials inserted at the metal/semiconductor interface provide an effective means to improve charge injection and reduce the threshold voltage for organic field-effect transistors. Here, we report the use of poly(2-alkyl-2-oxazoline) interlayers for gold electrodes within n-type poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] field-effect transistors. We specifically show that the use of poly(2-ethyl-2-oxazoline) yields a reduction in the work function from 5.07 to 4.73 eV (ΔE = 0.34 eV), an increase in the electron mobility from 0.04 to 0.15 cm²/V s (3.75 times), and a reduction in the threshold voltage from 27.5 to 16.5 V (ΔV = 11 V) relative to bare gold. The alkyl side chain of the poly(2-alkyl-2-oxazoline) has a significant influence on the film microstructure and, as a consequence, also device performance.