With the aim of achieving high efficiency, cost-effectiveness, and reliability of solar cells, several technologies have been studied. Recently, emerging materials have appeared to replace Si-based cells, seeking economic fabrication of solar cells. Thin-film solar cells (TFSCs) are considered strong candidates for this mission, specifically perovskite-based solar cells, reporting competitive power convergence efficiencies reaching up to 25.7%. Substantial efforts have been invested in experimental and research work to surpass the Si-based cells performance. Simulation analysis is a major tool in achieving this target by detecting design problems and providing possible solutions. Usually, a TFSC adopts p-i-n heterojunction architecture by employing carrier transport materials along with the absorber material in order to extract the photogenerated electrons and holes by realizing a built-in electric field. Eventually, this dependency of conventional heterojunction TFSCs on carrier transport layers results in cost-ineffective cells and increases the possibility of device instability and interface problems. Thus, the design of p-n homojunction TFSCs is highly desirable as an essential direction of structural innovation to realize efficient solar cell operation. In this review, a summary of the fundamentals of TFSC materials, recent design and technology progress, and methodologies for improving the device performance using experimental research studies will be discussed. Further, simulation analysis will be provided by demonstrating the latest research work outcomes, highlighting the major achievements and the most common challenges facing thin film homojunction solar cell structures and the methods to improve them.

In this paper, we have investigated the effect of gate underlap, while using semiconducting silicide material as a source region, on the ambipolar and high-frequency performance of Tunnel Field Effect Transistors (TFETs). We demonstrated how to suppress the ambipolar conduction and enhance the ON current without deteriorating the performance of high-frequency switching characteristics of the double gate TFET by using the combined two methods. The ON to OFF current ratio ( I _ON /I _OFF ) and subthreshold swing (SS) as figures of merit for DC performance have been investigated. The main analog performance parameters like the transconductance ( g _m ) and unit-gain cutoff frequency ( f _T ) are analyzed. Moreover, circuit level digital performance parameters like the fall propagation delay ( t _phl ) and overshoot voltage ( V _p ) are inspected when the proposed design is utilized in an inverter circuit. Impact of effective oxide thickness and traps arising from manufacturing process on DC, analog, and circuit level performance is also investigated. TCAD simulation results reveal a significant enhancement in DC, analog and digital performance parameters of the proposed heterojunction TFET over Si-TFET that makes the proposed design more advantageous in the field of analog and digital applications.

Silicon Germanium (SiGe) solar cells with different bandgaps are used in the fabrication of the crystalline-Si/SiGe (c-Si/SiGe) double-junction cell in order to enhance the performance of the c-Si single devices. The new device is simulated with SCAPS-1D by placing the c-Si junction on the top of the SiGe solar cell. Through this simulation, one can assess the performance of the c-Si/SiGe double-junction device. The upper c-Si cell achieved an efficiency of 16.66% with 40.5 $\mu \text{m}$ total thickness, while the lower cell SiGe achieved ~ 19% efficiency. By analyzing the current matching between both cells at different bandgaps for SiGe cell (1.097 eV, 1.016 eV, and 0.928 eV), a mismatch is found. But, when applying 0.882 eV bandgap for the lower cell with absorber thicknesses of 110, 100, 90, and 6.2 $\mu \text{m}$ , a matching is obtained between the two junctions. The efficiency of the designed cell is found ~ 24.7%, with a maximum current density of 30.25 mA/cm ² , achieved at an open circuit voltage of 1.01 V and a total thickness of 57.2 $\mu \text{m}$ . These results indicate that the double-junction device significantly exceeds the device performance by 7.6% with equal thickness of the optimized single-junction c-Si solar cell.

Free Space Optics (FSO) Communication has attracted the attention of the researchers in the last decade due to its high data rate, security, and low cost. Relay-assisted techniques are used to divide the distance to shorter hops in order to mitigate the effects of turbulence, weather attenuation, pointing error, and geometric loss. Choosing an active relay per time slot has been proven to enhance the performance of the system and decrease the loading effect on the system when compared to all active relays. This paper investigates the best relay that can be selected according to the source to relay (S-R) channel coefficient, relay to destination (R-D) channel coefficient, and source to destination (S-D) channel coefficient. A comprehensive comparison is applied to the three following cases: (a) Broadcast phase from source to relay to select the best (Proactive-Relay); (b) Broadcast phase from relay to destination after broadcasting to all relays then select (Reactive-relays); and, (c) Direct link from source-to-best relay-to-destination to conclude which method is better for different scenarios, such as turbulence regime, number of relays, different pointing error effect, and severity of S-R as compared to R-D and vice versa. The selection methods regard to four aspects: (1) Number of relays (two or three relays); (2) Distance between Source-Relay and Relay-Destination (D = 400–600 m, 500–500 m, and 600–400 m); (3) The different turbulence of Log-normal channel and Gamma-Gamma channel (with a refractive index coefficient( $C_n^2$ = 0.5 × 10⁻¹⁴, 2 × 10⁻¹⁴ and 5 × 10⁻¹⁴)); and finally, (4) Beam waist ${\omega }_z$ (pointing error).

In this work, we investigated the parameters for decorating multiwalled carbon nanotubes with iron oxide nanoparticles using a new, inexpensive approach based on wet chemistry. The effect of process parameters such as the solvent used, the amount of iron salt or the calcination time on the morphology, decoration density and nanocluster size were studied. With the proposed approach, the decoration density can be adjusted by selecting the appropriate ratio of carbon nanotubes/iron salt, while nanoparticle size can be modulated by controlling the calcination period. Pristine and iron-decorated carbon nanotubes were deposited on silicon substrates to investigate their gas sensing properties. It was found that loading with iron oxide nanoparticles substantially ameliorated the response towards nitrogen dioxide.