Comparative study of the photoresponse from tetracene-based and pentacene-based thin-film transistors

We report on the photoresponse from tetracene-based and pentacene-based thin-film transistors (TFTs) with semitransparent NiOx source/drain electrodes and SiO2∕p+-Si substrate. Both organic TFTs have been fabricated with identical channel thickness and device geometry. Compared with pentacene-based TFTs, the tetracene-TFT exhibited superior potentials as a photodetector in the visible and ultraviolet range although it showed a field mobility (μ=0.003cm2∕Vs) which is two orders of magnitude lower than that of the pentacene-based TFT (μ=∼0.3cm2∕Vs). The tetracene-TFT displayed a high photo-to-dark current ratio (Iph∕Idark) of 3×103, while that of the pentacene-TFT was only ∼10.