n-type carbon nanotube inks for high-yield printing of ultrabroadband soft photo-imager thin sheets

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.