Cu₃N is an earth abundant, indirect energy bandgap semiconductor, in which crystal imperfections such as N vacancies (V_N) and Cu interstitials (Cu_i), do not give rise to mid-gap states, but instead electronic states that are energetically located very close or inside the conduction and valence band edges respectively. Consequently, it has been proposed to be used as a defect tolerant semiconductor for energy conversion and the fabrication of solar cells, considering that bipolar doping is possible too. Besides, it has an anti-ReO₃ cubic crystal structure which makes it suitable for energy storage and the realization of batteries, so it is still an active topic of investigation.

In this talk I will describe the fundamental properties of Cu₃N which is necessary in order to understand how suitable it is for energy conversion and storage. We have observed the M and R direct energy band gaps of Cu₃N by ultra-fast pump-probe spectroscopy (UPPS), confirming that it has a ‘clean’ energy bandgap with no mid gap states in excellent agreement with density function theory calculations of the electronic band structure ¹. However, while Cu₃N exhibits ‘clean’ band gaps it has limited carrier lifetimes attributed to indirect, non-radiative, recombination via electronic states located very close to or inside the conduction and valence bands. Consequently, the original suggestions that it may be used as a defect tolerant semiconductor need to be interpreted accordingly.   Furthermore, I will describe how the direct energy band gaps are influenced by the incorporation of oxygen as well as iodine ² and finally review the potential use of Cu₃N for energy storage.

¹ M.Zervos, A.Othonos, M.Sergides, T.Pavloudis and J.Kioseoglou, J.Phys.Chem. C (2020). 

² M.Zervos, A.Othonos, T.Pavloudis, S.Giaremis, J.Kioseoglou, K.Mavridou, M.Katsikini, F.Pinakidou and E.Paloura, J.Phys.Chem.C (2021).

³ M.Sergides, M.Zervos and A.Othonos, J.Appl.Phys (2020).