Md. Suruz Mian

Amorphous tungsten oxide films are prepared on indium tin oxide/glass substrates using reactive magnetron sputtering and their electrochromic (EC) properties are investigated. To achieve the densely colored films, samples of 500 and 1000 nm thickness are deposited with different pumping speeds and oxygen flow rates at Ar 3 Pa atmosphere. The as‐deposited films are similarly transparent (≈80%), but their EC properties vary depending on the deposition conditions and strongly on film thickness. The 500 nm‐thick samples have a transmittance of 4–8% in the colored state, which recover well in the bleached state. In contrast, the 1000 nm‐thick films have very low transmittance (<1%) in the colored state but are not completely recovered. Among 1000 nm‐thick films, large pumping speed and a large oxygen flow rate condition result in comparatively better recoverability. The cyclic voltammograms of 500 nm films show small and balanced charge transfer, while those of 1000 nm films reveal large and unbalanced charge transfer. These indicate that more ions are intercalated into the 1000 nm samples but are not completely deintercalated. These findings contribute to the development of EC applications for light shielding.

<title>Abstract</title> The present work investigates a tin-based highly efficient perovskite solar cell (PSC) by a solar cell capacitance simulator in one dimension. Molybdenum disulfide is introduced as hole transport layer in the proposed solar cell device structure. The photovoltaic performances of the proposed solar cell are investigated by varying thickness, doping concentration, and bulk defect density of various layers. Furthermore, the operating temperature and the series and shunt resistances are analyzed systematically. A higher conversion efficiency of 25.99% is obtained at the absorber thickness of 2000 nm. The optimum doping density of 10¹⁷ cm⁻³ is estimated for the absorber, electron transport layer (ETL), and hole transport layer (HTL), respectively. The optimum thicknesses of 50 nm, 1000 nm, and 60 nm are also found for the titanium dioxide as ETL, methylammonium tin triiodide (CH₃NH₃SnI₃) as absorber layer, and molybdenum disulfide as HTL, respectively. The efficiency of the proposed lead-free CH₃NH₃SnI₃-based solar cell with the alternative molybdenum disulfide HTL is calculated to be 24.65% with open-circuit voltage of 0.89 V, short-circuit current density of 34.04 mA/cm², and fill-factor of 81.46% for the optimum parameters of all layers. These findings would contribute to fabricate low-cost, non-toxic, stable, and durable lead-free PSCs for the next generation.

<title>Abstract</title>In this study, copper bismuth oxide (CuBi₂O₄) absorber-based thin film heterojunction solar cell structure consisting of Al/FTO/CdS/CuBi₂O₄/Ni has been proposed. The proposed solar cell device structure has been modeled and analyzed by using the solar cell capacitance simulator in one dimension (SCAPS-1D) software program. The performance of the proposed photovoltaic device is evaluated numerically by varying thickness, doping concentrations, defect density, operating temperature, back metal contact work function, series and shunt resistances. The current density–voltage behaviors at dark and under illumination are investigated. To realize the high efficiency CuBi₂O₄-based solar cell, the thickness, acceptor and donor densities, defect densities of different layers have been optimized. The present work reveals that the power conversion efficiency can be enhanced by increasing the absorber layer thickness. The efficiency of 26.0% with open-circuit voltage of 0.97 V, short-circuit current density of 31.61 mA/cm², and fill-factor of 84.58% is achieved for the proposed solar cell at the optimum 2.0-μm-thick CuBi₂O₄ absorber layer. It is suggested that the p-type CuBi₂O₄ material proposed in the present study can be employed as a promising absorber layer for applications in the low cost and high efficiency thin-film solar cells.

© 2020 Author(s). In this study, we studied how to connect a thermoacoustic engine (TAE) and an impulse turbine to construct a thermoacoustic generator for converting thermal energy into electric power. The thermoacoustic generator was separated into two sub-systems: (1) system A, which consisted of a looped-tube TAE and a branch tube, and (2) system B, which consisted of an impulse turbine loop and a branch tube. The sub-systems were evaluated individually using an acoustic driver to determine the driving conditions such as branch length, driving frequency, and temperature for the connected system. In system A, which included the TAE, the change in specific acoustic impedance was small with respect to the velocity amplitude. However, in system B, which included the impulse turbine, the change in specific acoustic impedance with respect to the velocity amplitude was nonlinear. The sub-systems were connected by branch pipes, whose lengths were determined from the individual sub-system evaluation results, and the device was confirmed to self-oscillate at the driving temperature. When the device was operated at the driving conditions, the frequency, velocity amplitude, and specific acoustic impedance with self-oscillation were the same as those of the individual sub-systems. This also confirms the validity of evaluating the TAE and impulse turbine separately.