No abstract

The friction coefficient, wear rate, and wear coefficient of the aluminum metal surface were measured at room temperature (≈300 K) with a pin-on-disk machine at a fixed load of 196.2 N. Two different testing configurations were adopted: (1) aluminum pin vs. Helix oil-on-steel disk (AHS) and (2) aluminum pin vs. 10% Polytron plus 90% helix oil-on-steel disk (APS). In the AHS configuration, the wear of the aluminum surface was found to be approximately 70 μm; however, in the APS configuration the wear dropped to 20 μm, revealing a marked decrement of one-third of the wear of aluminum. The volume wear rate of the metal in the unaided Helix oil was estimated to be 1.28×10 -3 mm 3 /min. The additive minimized the volume wear rate of the aluminum metal by orders of magnitude to 6.08×10 -5 mm 3 /min. Similarly, the wear coefficient of the aluminum pin, calculated in the AHS configuration, rendered a value of 1.27×10 -10 m 2 /N. In the APS configuration, the same parameter was 4.22×10 -11 m 2 /N, that is to say, an order of magnitude lower than the preceding value. The observed coefficient of friction for aluminum is 0.012 in Helix oil and falls to a remarkably lower value of 0.004 through the Polytron additive. The experimental findings demonstrate that Polytron additive substantially lessens the wear of the aluminum surface; in effect, the wear coefficient and the wear rate decline linearly. This singularity may be linked to the ability of Polytron to impregnate the crystal structure of the metal due to its ionic character and the consequent adherence to the metallic surface as a hard surface layer.

Cadmium selenide (CdSe) thin films were grown on borosilicate glass substrates using the RF magnetron sputtering method. In this study, CdSe thin film was deposited at a deposition temperature in the range of 25 °C to 400 °C. The influence of deposition or growth temperature on the structural, morphological, and opto-electrical properties of CdSe films was investigated elaborately to achieve a good-quality window layer for solar-cell applications. The crystal structure, surface morphology, and opto-electrical characteristics of sputtered CdSe films were determined using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–Vis spectrophotometry, and Hall effect measurement, respectively. The XRD results revealed the polycrystalline nature of CdSe, with a hexagonal structure having a strong preferential orientation toward the (002) plane. As evident from the FESEM images, the average grain size and surface morphology of the films were dependent on deposition temperatures. The carrier concentration was obtained as 1014 cm−3. The band gap in the range of 1.65–1.79 eV was found. The explored results suggested that sputtered CdSe thin film deposited at 300 °C has the potential to be used as a window layer in solar cells.

The influence of Molybdenum diselenide (MoSe2) as an interfacial layer between Cu(In,Ga)Se2 (CIGS) absorber layer and Molybdenum (Mo) back contact in a conventional CIGS thin-film solar cell was investigated numerically using SCAPS-1D (a Solar Cell Capacitance Simulator). Using graded bandgap profile of the absorber layer that consist of both back grading (BG) and front grading (FG), which is defined as double grading (DG), attribution to the variation in Ga content was studied. The key focus of this study is to explore the combinatorial effects of MoSe2 contact layer and Ga grading of the absorber to suppress carrier losses due to back contact recombination and resistance that usually occur in case of standard Mo thin films. Thickness, bandgap energy, electron affinity and carrier concentration of the MoSe2 layer were all varied to determine the best configuration for incorporating into the CIGS solar cell structure. A bandgap grading profile that offers optimum functionality in the proposed configuration with additional MoSe2 layer has also been investigated. From the overall results, CIGS solar cells with thin MoSe2 layer and high acceptor doping concentration have been found to outperform the devices without MoSe2 layer, with an increase in efficiency from 20.19% to 23.30%. The introduction of bandgap grading in the front and back interfaces of the absorber layer further improves both open-circuit voltage (VOC) and short-circuit current density (JSC), most likely due to the additional quasi-electric field beneficial for carrier collection and reduced back surface and bulk recombination. A maximum power conversion efficiency (PCE) of 28.06%, fill factor (FF) of 81.89%, JSC of 39.45 mA/cm2, and VOC of 0.868 V were achieved by optimizing the properties of MoSe2 layer and bandgap grading configuration of the absorber layer. This study provides an insight into the different possibilities for designing higher efficiency CIGS solar cell structure through the manipulation of naturally formed MoSe2 layer and absorber bandgap engineering that can be experimentally replicated.