Influence of pre-annealing of printed silver electrodes on ultrafast laser ablation of short thin-film transistor channels on flexible substrates

Abstract

The cutoff frequency and current from an organic thin-film transistor (OTFT) is strongly dependent on the length and to some extent the uniformity of the transistor channel. Reducing the channel length can improve the OTFT performance by increasing the current and frequency. Picosecond laser ablation of printed Ag electrodes, compatible with roll-to-roll fabrication has been investigated. The ablation threshold was found to be similar for the laser wavelengths tested: 515 nm and 1030 nm. Short transistor channels could be opened both after light annealing at 70 o C and after annealing at 140 o C. The channels in the lightly cured films had significantly less scale formation which critical for avoiding shunts in the device. By moving from bottom electrodes fully defined by printing to bottom electrodes where the transistor channel is opened by laser, the channel length could be reduced from 40 µm to less than 5 µm.