Modification of N-doped graphene films and their applications in heterojunction solar cells

•A two-step growth process was developed to synthesis N-doped graphene films.•The inserted nitrogen atoms can solve the problem of carrier recombination.•The solar cells with more excellent characteristics of photovoltaic is obtained.•This work can further promote the development of graphene film in solar cell. A two-step growth process was developed to synthesis N-doped graphene films by using pentachlorop-yridine as nitrogen source and methane as carbon source. The configuration and compositions of modified graphene films were characterized by X-ray photoelectron spectroscopy (XPS), and its bonding properties were obtained with Raman spectroscopy. The films were found to be N-doped graphene films with the N/C ratio of 2.5%–4%. The electronic properties of the films have been tested by using Hall Effect Measurement System. The nitrogen doped graphene film exhibits lower resistance (7.26 × 10−6 Ω·cm) but smaller mobility (521.8 cm2/V·S). Current density-voltage feature of solar cells with different structures were measured to research the photovoltaic characteristic of Graphene/n-Si solar cells. It was found that solar cells with N-doped graphene layer shown better performance of photovoltaic in illumination. The maximum energy conversion efficiency achieved was 6.24%. The inserted nitrogen atoms can effectively reduce the resistivity of graphene films, thus solve the problem of carrier recombination which caused by slow transmission speed. As a result, N-doped graphene film can highly facilitate the transmission and exportation of current, along with the improvement of short-circuit current density, which further enhance the overall efficiency of the solar cells. This work can promote the development of graphene film in application of transparent conductive electrode fields.