Experimental and theoretical study of crystal structure and bandgap of CdBi2S4

In this study, we present a new way of solid state synthesis of single crystals of CdBi2S4. Moreover, we compare the results of both experimental and theoretical studies of crystal structure and energy bandgap of this compound. Obtained single crystals are characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The presence of single crystals of the title compound is confirmed by the X-ray diffraction studies. The resolved crystal structure agrees with the one already reported for CdBi2S4. SEM images show the compositional homogeneity of obtained crystals and EDX investigation confirms the elemental composition of CdBi2S4. Moreover, the Uspex algorithm is used for crystal structure prediction of this compound to check for potential polymorphs. Results of action of the Uspex algorithm suggest the existence of a new monoclinic phase different than that observed experimentally. Ab initio calculations were used to study the band structure of the theoretical crystal structure of CdBi2S4 using GGA-PBE and HSE06 approximations. The energy bandgap of bulk CdBi2S4 was also studied experimentally with the Tauc method, yielding a value of 1.42 ​eV, showing the potential of this compound for applications in photovoltaics.