Bismuth layered structure ferroelectrics (BLSFs), also known as Aurivillius phase materials, are ideal for energy-efficient applications, particularly for solar cells. This work reports the first comprehensive detailed theoretical study on the fascinating structural, electronic, and optical properties of XNb₂Bi₂O₉ (X = Ca, Ba, Be, Mg, Sr). The Perdew–Burke–Ernzerhof approach and generalized gradient approximation (GGA) are implemented to thoroughly investigate the structural, bandgap, optical, and electronic properties of the compounds. The optical conductivity, band topologies, dielectric function, bandgap values, absorption coefficient, reflectivity, extinction coefficient, refractive index, and partial and total densities of states are thoroughly investigated from a photovoltaics standpoint. The material exhibits distinct behaviors, including significant optical anisotropy and an elevated absorption coefficient > 10⁵ cm⁻¹ in the region of visible; ultraviolet energy is observed, the elevated transparency lies in the visible and infrared regions for the imaginary portion of the dielectric function, and peaks in the optical spectra caused by inter-band transitions are detected. According to the data reported, it becomes obvious that XNb₂Bi₂O₉ (X = Ca, Ba, Be, Mg, and Sr) is a suitable candidate for implementation in solar energy conversion applications.

Pseudo-tetragonal phase boundary existent Ca_0.60(Li_0.5Bi_0.5)_0.40Bi₂Nb₂O₉:xwt%MnO₂ (CBNL:xMn) ceramic series is fabricated to investigate the ferroelectric and piezoelectric properties. Pure CBNL and CBNL:xMn ceramics have maintained their pseudo-tetragonal phase boundary even after the insertion of Mn ions. The addition of MnO₂ in CBNL has improved the multifunctional properties of material at x = 0.20. CBNL:0.20Mn has shown the relative density of 98%, saturated polarisation (P_S) of ~ 13.5 µC/cm², high piezoelectric coefficient (d₃₃) of ~ 25 pC/N, and high impedance of ~ 8.9 × 10⁸ Ω at room temperature, which are the much improved values as compared to pure CBN or CBNL ceramics. The dielectric constant (ɛ_r) dependence on temperature is presenting the sharp peak of CBNL:0.20Mn ceramic at Curie temperature (T_C) ~ 918°C confirming the strong ferroelectric nature of the ceramic. Importantly, poled CBNL:0.20Mn ceramic has shown the thermally stable depoling performance, which remains 92% (23 pC/N) of its initial room temperature value even after annealing the sample at 800°C. Results indicate the clear significance that the introduction of multivalence Mn ions in the pseudo-tetragonal existent region of CBNL has improved the multifunctional properties of the material, making it a strong candidate to be utilised in actuators and high-temperature piezoelectric devices.

For the first time, density functional theory (DFT) calculations have been employed for the measurement of the structural, mechanical, optical, and electrical properties of a bismuth-layered structure ferroelectrics (BLSFs) family member possessing an orthorhombic structure with Cmc2₁ space group. Based on the exchange–correlation approximation, our calculations show that Pb₂Bi₄Ti₅O₁₈ possesses an indirect band gap, while the materials X₂Bi₄Ti₅O₁₈ (X = Ba, Ca, and Sr) demonstrate direct band gap, where the estimated density functional fundamental band gap values lie between 1.84 to 2.33 eV, which are ideal for photovoltaic applications. The optical performance of these materials has been investigated by tuning the band gaps. The materials demonstrated outstanding optical characteristics, such as high absorption coefficients and low reflection. They exhibited impressive absorption coefficient (α = 10⁵ cm⁻¹) throughout a broad energy range, especially in the visible spectrum (10⁵ cm⁻¹ region). The findings show that the compounds demonstrate lower reflectivity in the visible and UV regions, making them suitable for single-junction photovoltaic cells and optoelectronic applications. The Voigt–Reuss–Hill averaging technique has been employed to derive elastic parameters like bulk modulus (B), Young’s modulus, shear modulus (G), the Pugh ratio (B/G) and the Frantesvich ratio (G/B) at 0.1 GPa. The mechanical stability of the compounds was analyzed using the Born stability criteria. Pugh’s ratio and Frantesvich’s ratio show that all the compounds are ductile, making them ideal for flexible optical applications.

For the first time, we explored the optical, electronic, mechanical, and structural properties of the Ruddlesden–Popper phase family member X₂CaTa₂O₇ (X = Li, Na, K, and Rb) by using density functional theory (DFT) with the Perdew–Burke–Ernzerhof (PBE) function in the generalized gradient approximation (GGA) framework. These materials show promising potential for energy conversion applications. Detailed investigations into structural parameters, band gaps, total and partial densities of states, and optical and mechanical properties demonstrate their suitability for photovoltaic technologies. The calculated electronic band gap structures and density of states demonstrate that X₂CaTa₂O₇ (X = Li, Na, K, and Rb) are semiconductors in nature with band gaps ranging from 1.52 eV to 3.02 eV. Measurements demonstrate substantial contributions from O-2p⁴, Ca-4p⁴, and Ta-4f¹⁴ orbitals to the electronic structures of the compounds. Moreover, the optical characteristics, like the reflectivity, absorption coefficients (10⁵ cm⁻¹), dielectric functions (8.5), refractive index (2–3), and optical conductivity (4–6 fs⁻¹), highlight the abilities of these compounds for optoelectronic and photovoltaic devices. Additionally, the mechanical properties measurements of the compounds show that they are capable for flexible electronic applications as well. This manuscript provides good insights into the design and development of the compounds capable for next-generation photovoltaic devices.

For the first time, a theoretical investigation has been conducted into the structural, electrical, elastic, and optical properties of innovative bismuth-layered structure ferroelectric (BLSF) materials XTi₄Bi₄O₁₅ (where X = Sr, Ba, Be, and Mg). For all of the calculations, PBE-GGA and the ultra-soft pseudopotential plane wave techniques have been implemented with the DFT-based CASTEP simulation tool. Based on the exchange correlation approximation, the calculations reveal that XTi₄Bi₄O₁₅ (X = Sr, Ba, Be, and Mg) materials demonstrate direct band-gap semiconductor behavior with an estimated density functional fundamental gap in the range from 1.966 eV to 2.532 eV. The optical properties of these materials exhibit strong absorption and low reflection in the visible range. Moreover, the estimations of the elastic properties of the materials have shown mechanical stability and ductile behavior (due to B/G > 1.75), where G and B denote the shear modulus and the bulk modulus. Based on the above-mentioned highlights, it can be confidently stated that these materials are promising potential candidates for photovoltaic applications and solar cells due to their suitable direct band gap and high absorption coefficient.