Laser Direct Writing of Heteroatom (N and S)‐Doped Graphene from a Polybenzimidazole Ink Donor on Polyethylene Terephthalate Polymer and Glass Substrates

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 14; no. 44; pp. e1803143 - n/a
• Main Authors: Huang, Yihe, Zeng, Lei, Liu, Chongguang, Zeng, Desen, Liu, Zhu, Liu, Xuqing, Zhong, Xiangli, Guo, Wei, Li, Lin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.11.2018
• Subjects: Chemical properties; Dimethyl sulfoxide; Direct laser writing; Glass substrates; Graphene; Indium tin oxides; ink; Laser beams; Laser damage; laser direct writing (LDW); Lasers; nanocrystallization; Nanotechnology; Optical properties; Organic chemistry; PET; Photochemical reactions; Polybenzimidazoles; Polyethylene terephthalate; polymers; sheet resistance; Smart sensors; Tin oxides; Ultraviolet lasers; sheet resistance; laser direct writing (LDW); nanocrystallization; ink; polymers; PET; graphene
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201803143

In this paper, for the first time, a laser direct writing technique is reported to form S‐ and N‐doped graphene patterns on thin (0.3 mm thickness) polyethylene terephthalate (PET) and glass substrates from a specially formulated organic polybenzimidazole (PBI) ink, without thermally affecting the substrates and without the need for a metallic precursor. Unlike standard graphene ink printing, postcuring at high temperatures is not needed here, thus avoiding potential substrate distortion and damages. A UV laser beam of 355 nm wavelength is used to generate photochemical reactions to break the CS bond (2.8 eV) from dimethyl sulfoxide (DMSO, a component of the PBI ink) and the CN bond (3.14 eV) of PBI and form N‐ and S‐doped graphene on the substrates. The sheet resistance of the laser‐induced graphene is as low as 12 Ω sq−1 on PET, matching that of indium–tin oxide (ITO). The laser‐written doped graphene shows hydrophilic characteristics, unlike pristine graphene. The S‐ and N‐doped graphene allows the tailoring of bandgaps and thus controlling electrical and chemical properties. The optical transparency of the written graphene is below 10% which could be improved in the future. Potential applications include printing of flexible circuits and sensors, and smart wearables. Heteroatom (N and S)‐doped graphene patterns are written onto polymer and glass substrates using a picosecond laser to process specially formulated polybenzimidazole (PBI) ink. Excellent electrical property, comparable to indium–titanium oxide (ITO), and better than standard graphene inks are achieved through tailored nitrogen and sulfur doping. A good bonding of the doped graphene with the polymer substrate is demonstrated.