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High temperature conjugated polymer transistors
Organic semiconductors have been considered a promising candidate to replace Silicon-based inorganic semiconductors in our electronics due to their lightweight, high flexibility, and solution processability. Recently, conjugated polymers were shown to be functional at up to 200°C, expanding organic semiconductors application territory into high-temperature electronics, which sorely depends on wide-bandgap semiconductors. To push the operational temperature boundary of polymer transistors even further than 200°C, our understanding of temperature impacts on the materials and charge transport mechanism in such harsh conditions needs to be improved. Here, we study the high temperature effect on polymer transistors from two main directions: via molecular design and via device engineering. First, via sidechain design, we explored the impact of close π-π packing on the thermal stability of semiconducting polymers. We discovered that maintaining close π-π packing can lead to lower chain distortion, thus improving the polymer transistors' operational stability at high temperatures. Then we study the impact from device factor, specifically contact resistance in device behavior at extreme conditions. We found that the contact area is more susceptible to high temperatures than other regions in the channels and is the main reason for the degraded performance. We then propose a facile method to minimize the contact problem, to achieve stable devices at above 200°C. And last, we proposed a simple method to attain quasi-temperature independent charge transport in polymer transistors from room temperature to 140°C by simply applying a prolonged bias gate voltage before heating. This research expands our knowledge on charge transport in conjugated polymers at high temperatures and provides a guide to make conjugated polymer transistors for extreme conditions in the future.