Multifunctional analysis of CaX2Bi2O9 (X = Nb, V, Ta, and Pa) compound by first principles framework for photovoltaic applications

A detailed theoretical study employing the first-principles framework of density functional theory has been carried out to explore the structural and multifunctional properties, including electronic, optical, dielectric, and mechanical properties, of bismuth-layered Aurivillius phase materials with the composition CaX2Bi2O9 (X = Nb, V, Ta, and Pa) for potential solar energy conversion applications. This investigation highlights the use of energy approximations based on the generalized gradient approximation in conjunction with the Perdew–Burke–Ernzerhof functional to analyze these complex compounds. Exhibiting bandgaps within the range of 0.9–2.9 eV, these bismuth-layered structured ferroelectric (BLSF)-based materials reveal promising semiconducting behavior, making them suitable for solar energy conversion technologies. This study delves into the detailed analysis of the total and partial density of states to reveal their electrical characteristics. Optical properties, including the dielectric function, refractive index, reflectivity, absorption, and energy loss function, are determined using the Kramers–Kronig relations. Notably, the compounds exhibited high absorption coefficients (∼105 cm−1), underscoring their potential for applications in optical devices. Elastic properties such as bulk modulus (B), Young’s modulus (E), and shear modulus (G) are evaluated through the Voigt–Reuss–Hill averaging method, and mechanical stability is confirmed using the Born stability criteria. Furthermore, mechanical flexibility is assessed through the Pugh ratio (B/G) and Frantsevich ratio (G/B), demonstrating their suitability for use in flexible solar cell applications.