The progression of silicon technology acting as substratum for the betterment of future photovoltaics

To solve energy crisis, generation of clean and renewable energy sources are highly recommended. It not only solve energy‐related matters but also resolves environmental issues. A great number of renewable energy sources are present nowadays to resolve aforementioned issues, out of which photovoltaic modules is the preferable technology over others. Silicon is the native element to be used in photovoltaic module, due to its reasonable cost and band gap. The deciding parameters to harness solar energy to electricity rely upon solar irradiance and weather conditions. Here, we describe the rapid transformation of silicon as photovoltaic solar cell material that transfigured the photovoltaic industry. The photovoltaic industry initiated with monocrystalline silicon and multicrystalline silicon solar cell having conversion efficiency reached up to approximately 22.9% and 20.8%, respectively. The contemporary outburst for the trade of photovoltaic industry is due to the high manufacturing cost of silicon solar panels, which provided a chance for researchers to quest for advanced technology. It gave an opportunity for thin film solar cell to infiltrate in the market. This technology reduced the cost but on the expense of lower conversion efficiency.     

Dispersion in steady and time-oscillatory flows through an eccentric annulus

A multiple-scale perturbation is conducted to derive an averaged equation for predicting the longtime solute transport in an eccentric annulus in which the uniaxial flow may oscillate periodically in time. A proof for the positiveness of the dispersivity is presented, implying that over a cycle of oscillation a solute cloud always broadens. For a steady flow driven by a fixed pressure gradient, increasing the eccentricity and annulus size gives rise to stronger dispersion. This relationship holds when the flow becomes unsteady. In the limit of slow oscillation, dispersion due to an oscillatory flow asymptotes to one-half of that by a steady flow. Increasing the oscillation frequency leads to a two-step decay of the dispersivity. The maximum dispersion in an oscillatory flow can be achieved in the limit of slow oscillation and large eccentricity, where dispersion can be O(10³) times larger than that in an otherwise concentric annulus.     

Direct Formation of Titanium Carbide via In Situ Carbothermal Reduction of TiO2/Carbon Cladding for Coating Application

Protection of Metals and Physical Chemistry of Surfaces - In situ direct formation of titanium carbide (TiC) was realized via tungsten inert gas (TIG) arc surface cladding using titanium dioxide...     

Dynamic Recrystallization in Cu-Cr-Zr-Ti Alloy Under Large Plane Strain Conditions

Metallurgical and Materials Transactions A - The Cu-Cr-Zr-Ti alloy was subjected to single-hit plane strain compression tests in the temperature range of 923 K to 1073 K...     

An accurate and simplified small signal parameter extraction method for GaN HEMT

In this paper, development of a small signal model for 2 × 200 μm GaN HEMT based on the conventional 20-element model is presented. The proposed model presents a direct parameter extraction algorithm, instead of the hybrid optimization approach, that provides simplification, accuracy, and less computational complexity. The extrinsic elements are extracted using a modified cold pinch-off condition while discarding the unwanted forward biasing of the gate. The negative drain to source capacitance C_ds is also observed in the ohmic region (for smaller V_DS). An excellent agreement found between the measured and modeled data for a wide range of frequencies and bias values shows the effectiveness of the proposed approach. The proposed modeling technique is validated with a good agreement between the achieved bias dependency of intrinsic parameter values and the respective theoretical parameter values.     

Circumventing Dedicated Electrolytes in Light‐Emitting Electrochemical Cells

Light‐emitting electrochemical cells (LECs) are devices that utilize efficient ion redistribution to produce high‐efficiency electroluminescence in a simple device architecture. Prototypical polymer LECs utilize three components in the active layer: a luminescent conducting polymer, a salt, and an electrolyte. Similarly, many small‐molecule LECs also utilize an electrolyte to disperse salts. In these systems, the electrolyte is incorporated to efficiently conduct ions and to maintain phase compatibility between all components. However, certain LEC approaches and materials systems enable device operation without a dedicated electrolyte. This review describes the general methods and materials used to circumvent the use of a dedicated electrolyte in LECs. The techniques of synthetically coupling electrolytes, incorporating ionic liquids, and introducing inorganic salts are presented in view of research efforts to date. The use of these techniques in emerging classes of light‐emitting electrochemical cells is also discussed. These approaches have yielded some of the most efficient, long‐lasting, and commercially applicable LECs to date.     

A Highly Emissive Surface Layer in Mixed‐Halide Multication Perovskites

Mixed‐halide lead perovskites have attracted significant attention in the field of photovoltaics and other optoelectronic applications due to their promising bandgap tunability and device performance. Here, the changes in photoluminescence and photoconductance of solution‐processed triple‐cation mixed‐halide (Cs_0.06MA_0.15FA_0.79)Pb(Br_0.4I_0.6)₃ perovskite films (MA: methylammonium, FA: formamidinium) are studied under solar‐equivalent illumination. It is found that the illumination leads to localized surface sites of iodide‐rich perovskite intermixed with passivating PbI₂ material. Time‐ and spectrally resolved photoluminescence measurements reveal that photoexcited charges efficiently transfer to the passivated iodide‐rich perovskite surface layer, leading to high local carrier densities on these sites. The carriers on this surface layer therefore recombine with a high radiative efficiency, with the photoluminescence quantum efficiency of the film under solar excitation densities increasing from 3% to over 45%. At higher excitation densities, nonradiative Auger recombination starts to dominate due to the extremely high concentration of charges on the surface layer. This work reveals new insight into phase segregation of mixed‐halide mixed‐cation perovskites, as well as routes to highly luminescent films by controlling charge density and transfer in novel device structures.     

Linking Glass-Transition Behavior to Photophysical and Charge Transport Properties of High-Mobility Conjugated Polymers

The measurement of the mechanical properties of conjugated polymers can reveal highly relevant information linking optoelectronic properties to underlying microstructures and the knowledge of the glass transition temperature (T_g) is paramount for informing the choice of processing conditions and for interpreting the thermal stability of devices. In this work, we use dynamical mechanical analysis to determine the T_g of a range of state-of-the-art conjugated polymers with different degrees of crystallinity that are widely studied for applications in organic field-effect transistors. We compare our measured values for T_g to the theoretical value predicted by a recent work based on the concept of effective mobility ζ. The comparison shows that for conjugated polymers with a modest length of the monomer units, the T_g values agree well with theoretically predictions. However, for the near-amorphous, indacenodithiophene–benzothiadiazole family of polymers with more extended backbone units, values for T_g appear to be significantly higher, predicted by theory. However, values for T_g are correlated with the sub-bandgap optical absorption suggesting the possible role of the interchain short contacts within materials’ amorphous domains.