Improving the Performance and Uniformity of Carbon-Nanotube-Network-Based Photodiodes via Yttrium Oxide Coating and Decoating

Semiconducting single-walled carbon nanotube (SWCNT) thin film can be obtained by conjugated polymer wrapping sorting technique followed by solution deposition and can be utilized as channel materials of field-effect transistors and absorbing layer of photodiodes. However, after deposition process, there are still polymer molecules wrapping around nanotubes, remaining between nanotubes and remaining on the thin film surface, which will cause large nanotube-electrode resistance and tube-tube resistance. Here, we demonstrate an Yttrium oxide coating-and-decoating technique that can removes polymers only under electrodes and thus improves the performance of photodiodes without inducing new defects in device channel. Treating only contact area, the average short-circuit current of photodiode increases from 9.1 nA to 10.7 nA while the average open-circuit voltage increases from 0.25 V to 0.30 V. This method also improves device uniformity significantly.