This work presents a comprehensive numerical study for designing a lead-free, all-inorganic, and high-performance solar cell based on Cs₂TiI₆ halide perovskite with all-inorganic carrier transport layers. A rigorous ab initio density-functional theory (DFT) calculation is performed to identify the electronic and optical properties of Cs₂TiI₆ and, upon extraction of the existing experimental data of the material, the cell is designed and optimized to the degree of practical feasibility. Consequently, a theoretical power conversion efficiency (PCE) of 21.17% is reported with inorganic TiO₂ and CuI as carrier transport layers. The calculated absorption coefficient of Cs₂TiI₆ reveals its enormous potential as an alternative low-bandgap material for different solar cell applications. Furthermore, the role of different point defects and the corresponding defect densities on cell performance are investigated. It is found that the possible point defects in Cs₂TiI₆ can form both the shallow and deep defect states, with deep defect states having a prominent effect on cell performance. For both defect states, the cell performance deteriorates significantly as the defect density increases, which signifies the importance of high-quality material processing for the success of Cs₂TiI₆-based perovskite solar cell technology.

Graphene, a staggering material with amazing electrical properties is a unique solution for the implementation of Terahertz antenna. Graphene based patch antennas are gaining interest in the field of communication for its reduced size in micrometer range operating in the THz band. The selection of substrate material acts as a major performance controller as it regulates the resonant properties of the graphene patch antenna. A graphene based circular patch antenna is designed here for operating in the frequency range of 6.8-7.2 THz. We applied polyimide, quartz, silicon dioxide and silicon nitride as substrate materials and evaluated the performance of the patch antenna for individual substrate materials based on return loss, voltage standing wave ratio (VSWR), 3D and 2D radiation pattern with gain as output. The result shows that using polyimide as substrate material results in excellent performance with a gain of 16.7 dB as compared to other substrate materials.