Over 20-Year Ambient Air Stability of N-Channel Ladder Polymer Thin-Film Transistors

Significant efforts have been dedicated to understanding factors that influence electronic transport in semiconducting polymers and to improving the performance of related device applications (e.g. organic thin-film transistors, organic electrochemical transistors, etc.). However, insights into ambient air stability are often overlooked both at the device level and at the materials level, especially for n-type semiconducting polymers. In this talk, I will discuss our over two-decades efforts in tracking the air stability of organic thin-film transistors. We show that n-channel thin-film transistors based on ladder poly(benzimidazobenzophenanthroline) (BBL) remain functional even after more than 20 years of storage in ambient air environment, which is unprecedented for organic semiconductors. The mechanism underlying the observed remarkable air stability is explained from both molecular structure and device engineering perspectives. By combining electrical characterization and numerical modeling of the trap density of states (DOS), we also demonstrate an effective strategy to passivate any environment-induced charge carrier trapping states, tune the electronic structure of BBL, and fully recover the performance of BBL transistor devices to its pristine state. Our results not only demonstrate the remarkable ambient air stability of n-channel polymer thin-film transistors but also contribute important insights into the structure-property relationship essential towards designing next-generation semiconducting polymers that combine high charge transport properties with improved stability.