On the True Band Gap of the (CH3NH3)2Pb(SCN)2I2 Hybrid Perovskite: An Interesting Solar‐Cell Material

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2018-04, Vol.12 (4), p.n/a
• Main Authors: Clavijo Penagos, Josue I., Romero, Eduard R., Gordillo, Gerardo, Correa Hoyos, John M., Reinoso Sánchez, Miguel Á.
• Format: Article
• Language: English
• Subjects: Band gap; Crystal structure; Density functional theory; Kubelka–Munk function; Lead; Optical properties; perovskites; quantum espresso; Reflectance; semiconductors; solar cells; Solid state physics; X‐ray diffraction
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201700376

The hybrid halide perovskite methyl ammonium lead iodide thiocyanate – (CH3NH3)Pb(SCN)2I2 – is synthesized both as a powder and as a thin film. The crystal structure and key optical properties (band gap) are determined by diffuse reflectance spectra and X‐ray diffraction (Rietveld refinement) measurements and compared to density functional theory (DFT) state‐of‐the‐art calculations. It is found that the refined orthorhombic crystal structure presents 2D‐layer confinement, and that the optical band gap presented in this work does confirm some previous reports and rebuts other results, too. An appealing solar cell material (CH3NH3)2Pb(SCN)2I2, MAPSI, is a semiconductor with 2D‐layered structure and nearly direct band gap, showing unique electronic properties arising from the SCN− ion incorporation. For this material, both experimental measurements (diffuse reflectance, XRD) and DFT‐based calculations (band structure, density of states) confirm a wide band gap value, which is against previous reports.