Large enhancement of the photocurrent density in N-doped Cu3N films through bandgap reduction

Copper nitride (Cu3N) has attracted wide attention for solar energy conversion applications owing to suitable Egof 1.6–1.9 eV, non-toxicity, and possibility to fabricate homojunction solar cells. The Cu3N has a body-centered site of anti-ReO3structure, which can be easily occupied by transition metals. Hence, many studies on the band gap tuning of Cu3N have been conducted with doping of various elements. However, N-doped Cu3N film has not been reported experimentally yet although it was theoretically predicted to have very stable doping and new partially filled narrow band gap. Herein, via systematically controlling the nitrogen partial pressure (R= N2/N2+ Ar), we successfully fabricated N-doped Cu3N film using reactive RF sputtering. The N-doped Cu3N film (only specific R= 0.5) exhibits significantly reduced optical bandgap (1.1 eV) and improved photocurrent density (1.66 mA/cm2at 10 V) compared with that of pristine Cu3N film.