Evaluation of environmental effects on the performance of 2,8-difluoro 5,11-bis(triethylsilylethynyl) anthradithiophene thin-film transistors

The electrical performance of organic transistors has been known to suffer from exposure to high moisture and oxygen levels. Reduction of the carrier mobility, threshold voltage shifting to more negative gate voltages and appearance of a hysteresis loop when scanning the gate voltage in the forward direction and then backwards are all manifestations of transistor deterioration. The worst possible outcome would be that the transistor is not longer functional after prolonged exposure to air. The study was conducted using a bottom-gate bottom-contact transistor with 2,8-difluoro 5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES ADT) as the active layer. The top surface of the semiconductor was uncovered and the device characteristics were measured at different oxygen and humidity levels. We found out that the organic thin-film transistor performed better electrically in the absence of water vapor and oxygen. Moreover, the degradation was reversible if the source of water vapor and oxygen was removed. This demonstrate the importance of encapsulation in organic semiconductor devices.