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 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.