Performance recovery and optimization of poly(3-hexylthiophene) transistors by thermal cycling

We present the results of studies on the electrical and physical modifications to poly(3-hexylthiophene), upon thermal annealing. Thermally induced performance enhancements and thermal stability of polythiophene thin film transistors (TFTs) are explored. We observe substantial mobility improvements in devices annealed at low temperatures (<80°C), as well as increases in on/off ratios by more than two orders of magnitude at moderate anneal temperatures (∼120°C). We document changes in conductivity, mobility, on current, and on/off ratio with anneal temperature and total thermal budget. We are able to show the expulsion of environmental contaminants and increases in film density as means to performance recovery and enhancement. This study provides a comprehensive analysis of the effect of thermal cycling of polythiophene TFTs on various device performance metrics, and identifies relevant thermal limits and failure mechanisms.