Here, a prolytically controlled antioxidizing photosynthesis coenzyme, beta Nicotinamide adenine dinucleotide, reduced dipotassium salt (NADH) for a stable n-type dopant for carbon nanotube (CNT) transistors is proposed. A strong electron transfer from NADH, mainly nicotinamide, to CNTs takes place during pyrolysis so that not only the type conversion from p-type to n-type is realized with 100% of reproducibility but also the on/off ratio of the transistor is significantly improved by increasing on current and/or decreasing off-current. The device was stable up to a few months with negligible current changes under ambient conditions. The n-type characteristics were completely recovered to an initial doping level after reheat treatment of the device.