Speaker
Description
The path towards inexpensive solar cells for large-scale photovoltaic deployment is based on the utilisation of earth-abundant, non-toxic, and chemically stable materials. Among these, wide-bandgap semiconductors (1.6 -1.8 eV) are especially interesting as suitable partners for a bottom Si-based cell in tandem configuration. One promising candidate is BaZrS3, with a tunable direct bandgap, high absorption coefficient, and excellent air stability.
This work is focused on investigating the structural and vibrational properties of BaZrS3–BaZrO3 in order to develop predictive synthesis-structure-function relationships, which will bring this material to the forefront of PV.
A series of thin film layers was synthesized by annealing of BaZrO3 amorphous films in H2S atmosphere at various temperatures (700–1000 °C), resultin in samples with varying compositions (S/(S+O) from 0.2 to 0.8) and bandgaps of (2.0–3.4 eV). Lateral homogeneity of the thin films was confirmed by Scanning Electron Microscopy (SEM), electron-dispersive X-ray spectroscopy (EDX), and Raman mapping measurements. Transmission Electron Microscopy (TEM) of the cross-sections revealed the presence of phases at the back of the films, which were identified as BaZrO3. However, the near-surface area of each sample has shown high sulfur incorporation. This fact was exploited for obtaining reference Raman spectra of the BaZrS3-BaZrO3 film series with multiwavelength excitation sources (488, 532, and 785 nm). Detailed analysis of the spectra has revealed three types of modes, corresponding to Ba-Zr-S, Ba-Zr-O, and Ba-Zr-S-O type vibrations. This suggests possible presence of microdomains with primarily BaZrO3 and BaZrS3-like structures. Further investigation by a combination of TEM and EDX, as well as the microdomain influence on the optoelectronic properties is presented and discussed.
| Speaker Country | Switzerland |
|---|