Speaker
Description
ZnSnN$_{2}$ is an earth-abundant semiconductor with a predicted direct bandgap between 1.12-2.09 eV, based on DFT calculations.$^{1}$ Thus, it has been considered as a potential absorber material for solar cells. Recently, a numerical device simulation based on reported experimental material properties found a theoretical maximum efficiency of η ≈ 22% of for a ZnSnN$_{2}$ based solar cell.$^{2}$
Still, the fundamental study of structural properties of ZnSnN$_{2}$ is essential to facilitate the development of high-efficiency solar cells. Well crystallised bulk ZnSnN$_{2}$ is key to an in-depth study on its material properties, while thin-film ZnSnN$_{2}$ may hinder advanced studies due to preferred orientation and low crystallinity. However, the narrow stability region of ZnSnN$_{2}$ due to the small decomposition energy,$^{3}$ and the low decomposition temperature of ZnSnN$_{2}$$^{4}$ hamper the preparation of bulk ZnSnN$_{2}$.
In this work, we report a convenient pathway to obtain well-crystallised bulk zinc tin oxide nitrides as approximant towards ZnSnN$_{2}$ at ambient pressure and open the door to investigate structure-property relationships based on bulk samples. We achieved zinc tin oxide nitrides (Zn$_{1+x}$Sn$_{1-x}$N$_{2-2x}$O$_{2x}$) in the form of well-crystallised powder through a solid-state reaction route. This method further allows advanced characterisations that require bulk material and/or well-crystallised samples. We performed XRD experiments and interconnected it with a chemical analysis (XRF) to investigate the chemical composition and structural properties of the synthesised material. Using Raman spectroscopy, we compared the synthesised compound with reported ZnSnN$_{2}$ thin films.$^{5}$ The optical bandgap value of our powder material is in the range of the values reported by thin-film ZnSnN$_{2}$.$^{6}$ By correlating the synthesis conditions with the structural properties of the synthesised Zn$_{1+x}$Sn$_{1-x}$N$_{2-2x}$O$_{2x}$, we are now able to optimise the synthesis route. This will allow us to reduce the oxygen content in the material in a controlled way to obtain bulk ZnSnN$_{2}$ and tailor the materials properties.
Reference:
1. N. Feldberg, J. Aldous, W. Linhart, L. Phillips, K. Durose, P. Stampe, R. Kennedy, D. Scanlon, G. Vardar and R. Field III, Appl. Phys. Lett., 2013, 103, 042109.
2. A. Laidouci, A. Aissat and J. Vilcot, Sol Energy, 2020, 211, 237-243.
3. S. Chen, P. Narang, H. A. Atwater and L. W. Wang, Adv. Mater., 2014, 26, 311-315.
4. F. Kawamura, N. Yamada, M. Imai and T. Taniguchi, Cryst. Res. Technol., 2016, 51, 220-224.
5. P. C. Quayle, G. T. Junno, K. He, E. W. Blanton, J. Shan and K. Kash, Phys. Status Solidi B, 2017, 254, 1600718.
6. T. D. Veal, N. Feldberg, N. F. Quackenbush, W. M. Linhart, D. O. Scanlon, L. F. Piper and S. M. Durbin, Adv. Energy Mater., 2015, 5, 1501462.
