The immense demand for electrical energy motivated us to manipulate solar energy by means of conversion through solar cells (SCs). Advancements in photovoltaic (PV) technology are occurring very rapidly. In recent years, extensive research has been conducted on halide perovskite-based SCs because of their superior optoelectronic properties, enhanced efficiency, lightweight nature, and low cost. However, concerns have arisen regarding their longevity, stability, and commerciality due to the presence of toxic lead (Pb). The most prominent purpose of this investigation is to discover additional efficient, sustainable, and eco-friendly device architectures. In this study, we investigated an all-inorganic, lead-free rubidium germanium iodide (RbGeI₃)-based PSC device with the assistance of the SCAPS-1D simulator. Several electron transport layers (ETLs) and hole transport layers (HTLs) were incorporated with the perovskite layer, and an efficient primary structure was discovered. Then, the impact of temperature; back metal work function; series and shunt resistance; surface recombination velocity of carriers; thickness of the perovskite absorber layer, electron transport material (ETM), and hole transport material (HTM); carrier concentration of the perovskite absorber layer, ETM, and HTM; defect density of the perovskite absorber layer, ETM, and HTM; and defect density of the HTL/absorber and absorber/ETL interfaces on the PV performance of the proposed PSC device was analyzed. The optimized device exhibited a power conversion efficiency (PCE) of 30.35%, with superior values for open circuit voltage (V_oc), short circuit current density (J_sc), and fill factor (FF) of 1.067 V, 33.15 mA cm⁻², and 85.82%, respectively. The investigations in this study may be valuable and impactful to solar cell material researchers and move the research interest forward by one step so that experimental work with non-toxic RbGeI₃-based PSC devices will be performed in the future.

A novel structure of chalcogenide-based antimony selenide (Sb₂Se₃) which is the most promising absorber materials in the field of thin film solar cells with a tungsten diselenide (WSe₂) back surface field (BSF) has been proposed in this paper. Antimony selenide (Sb₂Se₃) with a BSF has been observed by one-dimensional solar cell capacitance simulator (SCAPS-1D). Its recognizable properties make it one of the most usable for non-toxic solar cell absorbers. This paper demonstrated the planning and modeling of Al/FTO/n-TiO₂/p-Sb₂Se₃/Ni (without BSF) and Al/FTO/n-TiO₂/p-Sb₂Se₃/p⁺-WSe₂/Ni (with BSF) structures. The capability of Al/FTO/n-TiO₂/p-Sb₂Se₃/p⁺-WSe₂/Ni heterojunction solar cell structure shows the promising performances. We have numerically simulated and observed the performance parameters such as power conversion efficiency (PCE), open circuit voltage (V_OC), short circuit current density (J_SC) and fill factor (FF) by tuning the different parameters such as thickness, doping concentration, defect density, the interface defect density, surface recombination velocity, series and shunt resistances along with temperature. The PCE of 20.61% with an absorber’s thickness of 800 nm for without BSF has been achieved. By inserting the WSe₂ BSF with thickness of 100 nm, highly improving efficiency of 32.35% has been demonstrated. Our simulation and numerical analysis also provide valuable and important information that is very effective for further implementation and achieving high efficiency of thin film solar cell.

Coronavirus disease 2019 (COVID-19) has made a huge pandemic situation in many countries of the world including Bangladesh. If the increase rate of this threat can be forecasted, immediate measures can be taken. This study is an effort to forecast the threat of present pandemic situation using machine learning (ML) forecasting models. Forecasting was done in three categories in the next 30 days range. In our study, multiple linear regression performed best among the other algorithms in all categories with R2 score of 99% for first two categories and 94% for the third category. Ridge regression performed great for the first two categories with R2 scores of 99% each but performed poorly for the third category with R2 score of 43%. Lasso regression performed reasonably well with R2 scores of 97%, 99% and 75% for the three categories. We also used Facebook Prophet to predict 30 days beyond our train data which gave us healthy R2 scores of 92% and 83% for the first two categories but performed poorly for the third category with R2 score of 34%. Also, all the models’ performances were evaluated with a 40-day prediction interval in which multiple linear regression outperformed other algorithms.

ZnTe thin films were synthesised and deposited on glass substrate for use as an absorber layer in TFSCs. The highest PCE is found 17.45% with V _oc of 1.41 V, J _sc of 14.01 mA cm ⁻² and FF of 88.53% for the 1184 nm thickness and 1.77 eV band gap of ZnTe which was annealed at 400 °C.

The demand for compact, lightweight, and high-performance antennas has increased in recent times in the communication industry. Microstrip patch antenna (MPA) becomes a better choice to effectively fulfill these requirements. In this study, hybrid techniques of partial ground plane, slotted patch, and defective ground structure are employed in MPA design to reduce the return loss, good impedance matching, and increased the bandwidth, gain, and efficiency of the antenna. This research demonstrates the impact of altering the feed point position, a crucial phenomenon of antenna design, on the patch antenna and determines the proper feed point location by comparing a minimum return loss (S11) which achieves the highest performance for the designed antenna. High-frequency structure simulator (HFSS) software is used to design and simulate the patch antenna. The operating frequency of the antenna is 6.85 GHz for UWB applications (3.1–10.6 GHz). A FR4 epoxy substrate material with dimensions of 30 mm × 20 mm is used to design the antenna. It has a dielectric constant of 4.4, a thickness of 0.8 mm and a tangent loss of 0.02. Multiple resonant frequencies are observed with different return losses for each feed location. The analysis shows that the finest feeding point is found at the center of the patch (9, 0) with a very low return loss (-28.35 dB), and a high impedance bandwidth (19.7 GHz). The antenna also achieved a gain of 4.46 dB, a directivity of 4.6904 dB, and a radiation efficiency of 95.90%. Hence, the location of the feed point can be considered as an influential factor in the antenna design.