|Mr. Lee A. Burton (Department of Chemistry, University of Bath, UK)
|Towards Hight Efficiency Tin Sulfide Solar Cells
|慶應義塾大学 理工学部 矢上キャンパス内
|Towards High Efficiencyve to find an abundant, cheap and environmentally benign semiconducting materials has never been greater, and tin sulfide is possibly the most exciting candidate. However, tin sulfide has presented a challenge to solid-state scientists for over half a century due to the high sensitivity of the structure, composition and material properties on synthesis conditions. A recent revival in interest has accompanied the isolation of novel conformations of tin sulfide in nanoparticles and thin films that could be of interest for photovoltaic applications.1 Thus far, exploration in this field has been predominantly empirical, with synthetic methods related directly to electronic or optical properties, without addressing fundamental materials chemistry.
We employ a combination of first-principles calculations and growth of single crystal materials to study the multiphasic tin sulfide system. Our methods provide insight into thermodynamic stabilities, reaction pathways and electronic configurations, which allow us to ultimately comment on the photovoltaic applicability of a given structure. We are also able to predict the spectra of the different phases and suggest optimal experimental techniques to discern between them.
Our key results to date can be summarised as follows:
• Our level of theory reproduces the known low temperature orthorhombic phase of SnS as the ground state (Figure 1).
• Despite reports of a zinc-blende phase of SnS in many studies,3 our work predicts that it is unstable and would spontaneously distort under moderate conditions (e.g. 350K), with large negative phonon modes.
• The enthalpies of formation, oxidation and sublimation for each phase.
• The distinct electronic structures of SnS, SnS2 and Sn2S3 can limit solar cell performance.