Crystal structure design and multiband physical properties of quaternary sulfide Ba5Bi2Co2S10 for optoelectronic conversion

Abstract

Multiband materials have received increasing attention due to their superior solar absorption properties. Here we design a new multiband compound, namely Ba₅Bi₂Co₂S₁₀, which crystallizes in the space group C²_2h-P2₁/m (No. 11) of the monoclinic system. Ba₅Bi₂Co₂S₁₀ is composed of one-dimensional ¹_∞[Bi₂Co₂S₁₀]¹⁰⁻ chains along the a axis. The adjacent chains are separated by Ba²⁺ ions. The optical band gap of the compound is 1.05 eV and 0.74 eV, presenting typical multi-absorption characteristics. First-principles calculations, which are perfectly consistent with the experimental results, show that the hybrid coupling effect between Co and S gives rise to multiband characteristics. Evident optoelectronic conversion properties were observed under visible light illumination with a photocurrent density of 4.0 mA cm⁻² at 1 V.