Copper interstitial recombination centers in Cu3N

Abstract

We present a comprehensive study of the earth-abundant semiconductor ${\mathrm{Cu}}_{3}\mathrm{N}$ as a potential solar energy conversion material, using density functional theory and experimental methods. Density functional theory indicates that among the dominant intrinsic point defects, copper vacancies ${\mathrm{V}}_{\mathrm{Cu}}$ have shallow defect levels while copper interstitials ${\mathrm{Cu}}_{\mathrm{i}}$ behave as deep potential wells in the conduction band, which mediate Shockley-Read-Hall recombination. The existence of ${\mathrm{Cu}}_{\mathrm{i}}$ defects has been experimentally verified using photothermal deflection spectroscopy. A ${\mathrm{Cu}}_{3}\mathrm{N}$/ZnS heterojunction diode with good current-voltage rectification behavior has been demonstrated experimentally, but no photocurrent is generated under illumination. The absence of photocurrent can be explained by a large concentration of ${\mathrm{Cu}}_{\mathrm{i}}$ recombination centers capturing electrons in $p$-type ${\mathrm{Cu}}_{3}\mathrm{N}$.