A low-temperature solution route for the synthesis of single crystals of BaSe3 and its photovoltaic study†

Cadmium chalcogenides are excellent materials for solar cell applications but are also toxic. Thus, new environmentally friendly metal chalcogenides with good photovoltaic properties need to be developed for sustainable applications. Herein, we describe the preparation of red-colored crystals of BaSe₃ using a low-temperature solution route for the first time. The BaSe₃ structure was determined and refined using a single-crystal X-ray diffraction study. The tetragonal BaSe₃ (space group: P2₁m) phase has cell constants of a = b = 7.2871(3) Å and c = 4.2516(3) Å. The chemical bonding in the BaSe₃ structure can be described using the Zintl–Klemm concept. The Ba atoms of the structure donate electrons to the Se atoms to form the trimeric Se₃²⁻ Zintl anions. We have investigated the physical properties of a polycrystalline BaSe₃ sample, which was synthesized at high temperatures via a reaction of pure elements. The sample is a semiconductor with direct and indirect optical bandgap energies of 1.7(2) eV and 1.6(2) eV, respectively, as estimated using the Tauc plot method. The polycrystalline BaSe₃ sample's total thermal conductivity (κ_tot) is 1.07 W m⁻¹ K⁻¹ near room temperature, which gradually drops to 0.47 W m⁻¹ K⁻¹ on heating the sample to 773 K. The photovoltaic studies of the material, BaSe₃, show a 20.4% increment in efficiency with its inclusion in the TiO₂/CdS photoanode due to enhanced light-harvesting and suppressed recombination at the photoanode/electrolyte interface.