First-Principles Study of Ferroelectric and Optical Properties in Derivatives of Thiourea...

Organic ferroelectric materials in the form of molecular crystals are promising alternatives to well-known ferroelectric perovskite oxides due to their structural flexibility, tunability, and ease of processing. First-principles density functional theory calculations combined with group theory analyses are employed in this work to discuss polar nature of a class of derivatives of thiourea: CH4N2A where A = O, S, Se, and Te. Optical properties in the UV range along with thermodynamic and dynamic stability of such materials are also evaluated in the study. We find that CH4N2Te with bandgap energy of ∼3.33 eV shows large spontaneous polarization of P = 10.92 μC/cm2. The electronic and optical properties become tunable under strain.