| AVS 61st International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Films Poster Session |
| Presenter: | Jacob Cordell, Penn State University |
| Authors: | R.E. Banai, Penn State University J.J. Cordell, Penn State University J.R. Nasr, Penn State University R.E. Urena, Penn State University N.J. Tanen, Penn State University J.R.S. Brownson, Penn State University M.W. Horn, Penn State University |
| Correspondent: | Click to Email |
Tin (II) Monosulfide (SnS) has become an interesting new material for thin film photovoltaics (PV). The optoelectronic properties indicate that SnS is a suitable material for PV. Its high absorption coefficient, greater than 104 cm-1, and band gap near 1.3 eV are well matched with the solar spectrum. SnS also has a carrier concentration greater than 1015 cm-3 and potential to be both n-type and p-type. With recent success in achieving 4% efficiency, SnS-based devices demonstrated their potential. However, the success comes with extensive optimization of each layer in the device, suggesting that further understanding of SnS is crucial to improving performance.
Sulfur is more volatile than tin and despite strong Sn-S bonds in tin sulfide compounds, sulfur loss to the gas phase while annealing in a vacuum environment. Therefore, it is important to start with a sulfur-rich thin film prior to annealing. Annealing of sulfur-rich sputtered tin sulfide thin films has not been done before. This work will investigate the optoelectronic properties, composition and morphology of annealed, sputtered tin sulfide thin films. Specifically, we will investigate the change in phase and improvement in material quality as a result of post-deposition heat treatments.
Tin sulfide thin films are sputtered on glass and silicon substrates from a distance of 11.5 cm at 115 W with a Ar chamber pressure of 10 mTorr. The sputter target was a 3” SnS2 with 99.999% purity (LTS Research Laboratories, Inc.). SnSx samples are deposited at room temperature and 150ºC. These samples are then annealed some under medium vacuum (<2x10-6 Torr) in the deposition chamber without breaking vacuum at 200, 300, and 400°C.
Preliminary results show promise for high-quality SnS thin films. Significantly improved crystallinity was seen in sulfur-rich thin films annealed at 400ºC for 30 minutes. Morphology is not the same for film deposited with and without substrate heating, although both film exhibit a uniform SnS phase as determined by X-ray diffraction. Longer anneal times are expected to further improve crystal quality. Reasonable resistivities are seen in these annealed thin films. The presentation will include details on producing high-quality SnS thin films as well as detailed results of optoelectronic properties, composition and morphology.