The development of a simple fabrication method for solution-based organic n-type dopant is of great importance for realizing low-cost complementary organic electronic devices. In addition, a heating-free doping process for organic electronic devices is highly promising for use in flexible electronics compatible with plastic substrates. In this study, we have developed a simple fabrication method of a high-performance n-type organic dopant using an organic cationic dye and a reducing agent. After coating the dopant solution on targeted materials, the organic non-polar solvents are removed by treating the vacuum at 1 × 10-3 torr without any annealing steps. The work function of graphene is changed from 4.5 eV to 3.98 eV after solution doping at room-temperature. The multiple coating of rPyB on graphene field-effect transistors (GFETs) results in long-term air-stability, revealing that the electron mobility is maintained for 90 days in ambient condition. Also, by using graphene electrodes doped with the organic dopant, the electronic performance of n-type organic filed-effect transistors (OFETs) can be improved because of well-balanced energy levels between the electrodes and the semiconducting layer. We also demonstrate a highly efficient selective stamping method for n-type molecular doping of a large-area 16 × 16 GFET array using a polydimethylsiloxane (PDMS) stamp and the reduced cationic dye. Our findings demonstrate an important methodology for the cost-effective synthesis of n-type dopants and their versatile use for the modulation of electronic performance in graphene and organic electronics.