Effect of Argon on the Properties of Copper Nitride Fabricated by Magnetron Sputtering for the Next Generation of Solar Absorbers

Abstract

Copper nitride, a metastable semiconductor material with high stability at room

temperature, is attracting considerable attention as a potential next-generation earth-abundant thinfilm

solar absorber. Moreover, its non-toxicity makes it an interesting eco-friendly material. In this

work, copper nitride films were fabricated using reactive radio frequency (RF) magnetron

sputtering at room temperature, 50 W of RF power, and partial nitrogen pressures of 0.8 and 1.0 on

glass and silicon substrates. The role of argon in both the microstructure and the optoelectronic

properties of the films was investigated with the aim of achieving a low-cost absorber material with

suitable properties to replace the conventional silicon in solar cells. The results showed a change in

the preferential orientation from (100) to (111) planes when argon was introduced in the sputtering

process. Additionally, no structural changes were observed in the films deposited in a pure nitrogen

environment. Fourier transform infrared (FTIR) spectroscopy measurements confirmed the

presence of Cu–N bonds, regardless of the gas environment used, and XPS indicated that the

material was mainly N-rich. Finally, optical properties such as band gap energy and refractive index

were assessed to establish the capability of this material as a solar absorber. The direct and indirect

band gap energies were evaluated and found to be in the range of 1.70–1.90 eV and 1.05−1.65 eV,

respectively, highlighting a slight blue shift when the films were deposited in the mixed gaseous

environment as the total pressure increased.