2022 journal article
Ultrathin P(NDI2OD‐T2) Films with High Electron Mobility in Both Bottom‐Gate and Top‐Gate Transistors
Advanced Electronic Materials.
Ultrathin organic films (typically < 10 nm) attracted great attention due to their (semi)transparency and unique optoelectronic properties that benefit applications such as sensors and flexible electronics. At the core of that, achieving high mobility in an ultrathin film is essential for the efficient operation of relevant electronic devices. While the state-of-the-art material systems, e.g., P(NDI2OD-T2) also known as N2200 can achieve high mobility in a thin film (typically > 20 nm), multitudinous challenges remain in processing an ultrathin film exhibiting desired charge transport morphology within a preferred thickness limit. Here, high electron mobility (a tenfold increase compared to annealed spin-coated films) is reported in both the top and bottom-gate configuration organic field-effect transistors comprising ultrathin N2200 films produced with a water-floating film transfer method. A range of characterization techniques are used to investigate these ultrathin films and their microstructure, and conclude that favorable edge-on polymer orientation at the top as well as throughout the ultrathin film thickness and the quality of π–π ordering as captured by the largest coherences length resulted in this high mobility in N2200 ultrathin films, in stark contrast to the commonly observed microstructural gradient in spin-coated thin films. The results provide new insight into the electronic and microstructural properties of thin films of organic semiconductors.