n‐type carbon nanotube inks for high‐yield printing of ultrabroadband soft photo‐imager thin sheets
Leo Takai, Yuya Kinoshita, Norika Takahashi, Minami Yamamoto, Daiki Shikichi, N. Izumi, Yuto Matsuzaki, Yukito Kon, Naoko Hagiwara, Yukio Kawano, Kou Li
Abstract
Abstract Photo‐thermoelectric (PTE) conversion with soft carbon nanotube (CNT) thin‐films potentially facilitates non‐destructive inspections as image sensor devices through ultrabroadband optical monitoring and freely attachable 3D omni‐directional views. Toward real‐time and large‐area measurements, printing fabrication methods are effective for multi‐pixel integrations of all‐solution‐processable CNT film PTE sensors. However, the conventional printing method of CNT PTE sensors yields fatally low‐efficient in fabricating each pixel due to insufficient diffusion of n‐type liquid dopants on the pristine p‐type film channels. Herein, this work demonstrates high‐yield fabrications of pn‐junction type PTE sensors by employing p‐/n‐type CNT inks. For such conceptualization, the presenting strategy first develops all‐solution‐processable n‐type CNT inks. Specifically, this work fabricates the n‐type inks by simply mixing the pristine p‐type CNT source solution and chemical liquid agents (hydroxide and crown‐ether) at high‐yield via ultrasonic vibration. The presenting CNT solution functions stability as n‐type materials on various supporting substrates by several fabrication methods in the counterpart junction with pristine p‐type film channels. Available fabrication methods and formable substrates are as follows: printing (screen, air‐jet dispense), coating (spin, casting), and manual application on papers, polymer sheets (parylene, polyimide, polyurethane, and polyethylene terephthalate), glass, and semiconductor wafers. Furthermore, the all‐solution‐processable pn‐junction CNT film PTE sensor fabricated by printing of p‐/n‐type inks sufficiently satisfies superior inherent optical properties. Following these, the presenting uniform high‐yield pn‐junction fabrication, 100 % forming at an error ratio of response signal intensities within 8.54 %, potentially facilitates large‐scale integrations of ultrabroadband deformable thin‐film PTE sensor sheets and the associated functional non‐destructive inspections.