Speaker
Description
Earth-abundant and low-cost materials are essential for future large-scale deployment of thin-film photovoltaics. However, many such materials face numerous challenges as the optimal performance requires fine-tuning of optoelectronic properties, which is usually achieved through defect engineering. Defect identification is a first step in this direction. This work gives an example of systematic defect identification in zinc phosphide (Zn3P2) using both theoretical and experimental perspectives that can be readily transferred to other materials.
Zn3P2 is an earth-abundant, direct bandgap (1.5 eV) and highly absorbent semiconductor, making it promising for PV applications. To solve the biggest challenge of defect engineering, we have employed Raman spectroscopy and density functional theory (DFT) calculations in order to identify and understand the effect of defects on materials properties.
First part of the study is focused on an comprehensive analysis of vibrational properties of tetragonally-structured Zn3P2 through DFT calculations and Raman measurements on single crystalline nanowires.[1,2,3] A total of 34 peaks were identified and assigned to 8A1g+9B1g+3B2g+14Eg theoretically predicted eigenmodes. These are assigned to a distinct vibrational patterns, involving vibrations of either Zn or P atoms primarily.
These results were used as a reference for the second part of the study, where a series of epitaxial single crystalline thin films with various Zn/P compositional ratios was produced. Comparison of the Raman spectra from the non-stochiometric samples has allowed identifying modes which intensity is sensitive to presence of various compositionally induced defects. This has allowed formulation of a general methodology for defect identification in Zn3P2 and other semiconductors, which will be presented and discussed.
[1] E. Stutz, Nanotechnology 32, 085704 (2021)
[2] S. Escobar Steinvall, Nanoscale Horizons, 5,274, (2020)
[3] S. Escobar Steinvall, Nanoscale Adv.,3, 326-332 (2021)
| Speaker Country | Switzerland |
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