Structural, Electronic, Optical, and Mechanical properties of BaTiO₃ Under Pressure: Using Fitting Tools to Create Predictive Functions for Mechanical Properties in Photovoltaic and 3D Printing Applications

Abstract

BaTiO3 is a model perovskite oxide that holds promise for high efficiency photovoltaic devices and next-generation 3D printing because it can have tunable optoelectronic and mechanical properties. In this work, we utilized density functional theory calculations with the CASTEP code and explored BaTiO3 under hydrostatic pressure. Our simulations illustrate that pressure is accompanied by a strong tendency for significant structural contractions that are characterized by lattice parameter shrinkage, and bond lengths reductions. The electronic band gap is highly dependent upon pressure; 1.71 eV (indirect, M–G) at 0 GPa, followed by 1.94 eV at 100 GPa, then reduced to 1.64 eV at 200 GPa, and consistently lowered to 1.34 eV at 300 GPa and then narrowed to around 0.91 eV at 400–500GPa. These band gap alterations pushed the optical absorption edge to wavelengths which are more favorable for photovoltaic applications. Device simulations using SCAPS-1D of photovoltaic devices under pressure, also demonstrated improved performance under pressure. At 0 GPa, the device has a power conversion efficiency (PCE) of 15.23% with an open-circuit voltage (Voc) of 0.7664 V, a short-circuit current density (Jsc) of 24.73 mA/cm², and a fill factor (FF) of 80.34%. As pressure is applied, these parameters significantly increased: at 300 GPa, Voc improved to 0.7729 V, Jsc increased to 30.40 mA/cm², FF is 79.39%, PCE improved to 18.65%; at 400 GPa, Voc improved to 0.7840 V, Jsc was 45.61 mA/cm², FF was 84.53%, and PCE improved to 30.23%, and similar values were observed at 500 GPa. With the elastic constants determined, it can be seen that the measured stiffness increased, and the favorable trend toward higher ductility increased as pressure was applied and is in support of incorporating BaTiO3 into mechanically resilient 3D-printed parts. All of this points to pressure engineering as a viable method for optimizing BaTiO3 for multifunctional optoelectronic and advanced manufacturing applications.