Light Induced Recovery of Polymer Field Effect Transistors

We have used differential terahertz spectroscopy to monitor performance degradation in state-of-the-art polymer field effect transistors (pFETs) based on poly[(9,9-dioctylfluorene-2,7-diyl)-co-(bithiophene)] (F8T2). After extended periods of operation holes are trapped in the polymer, increasing the device´s threshold voltage. We monitor the trapped charge density using THz spectroscopy, and investigate the device´s recovery as trapped holes are thermally removed. Illuminating the devices for a period with above-bandgap photons leads to a change in the terahertz transmission through the device, which is short lived after switching the light off.