Designing Photon Absorbing Materials by Cation Substitutions for Photovoltaics*

Recently, significant research efforts have focused on emerging solar cell technologies such as organic solar cells, perovskite photovoltaics, etc. However, these technologies face many challenges. In this talk, we will present a new family of light absorbing materials so-called pyroxene silicates. These materials are abundantly present in the earth crust, however, bandgaps of naturally formed pyroxene silicates such as NaAlSi₂O₆ are quite high ~5 eV. Therefore, it is important to find a way to reduce bandgaps below 3 eV to make them usable for optoelectronic applications¹. Using first-principles calculations we investigated the possibility of band structure engineering of pyroxene silicates with chemical formula A⁺¹B⁺³Si₂O₆ by proper cation substitution (A⁺= Na, PH₄⁺, SH₃⁺, CH₃PH₃⁺, CH₃SH₂⁺ and B³⁺ = Al³⁺ Ga³⁺, Tl³⁺). We found that appropriate substitutions of both A⁺ and B³⁺ cations can reduce the electronic bandgaps of these materials to as low as 1.31 eV. In this talk, we will also discuss in details how the bandgap is tailored in this class of materials with emphasis on the impact of our bandgap engineering on thermodynamic stabilities.
1. F. El Mellouhi, et al., ChemSusChem 10 1931 (2017).