Full in silico DFT characterization of lanthanum and yttrium based oxynitride semiconductors for solar fuels

Abstract

Finding new solar-energy absorber materials is one of the most significant challenges in artificial photosynthesis. Starting from the experimentally available LaTaON₂ and LaTiO₂N oxynitrides, we use DFT to propose new sunlight absorbing semiconductors. The synthetically unknown YTaON₂ and YTiO₂N are semiconductors with indirect band gaps of 2.7 eV and 2.9 eV, respectively. For the first time, we compute within Boltzmann transport theory the DOS-averaged effective mass and mobility of LaTaON₂, LaTiO₂N, YTaON₂ and YTiO₂N. Our first principles calculations indicate that the Y-based materials possess advantageous dielectric (ε_r ≥ 47), optical (α ≥ 10⁴ cm⁻¹ near band edge), and charge transport properties (m_e,h*_DOS ≈ 0.2; μ_e,h ≈ 10² cm² V⁻¹ s⁻¹) for the conversion of solar energy into storable fuels. Herein, our work leads to the complete in silico design of semiconductors for water splitting.