Nanoparticle process optimisation for plasmonic enhanced light trapping in polycrystalline silicon thin film solar cells

Thin film photovoltaics (PV) can potentially have a lower manufacturing cost by minimising the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometres thick, while crystalline Silicon (c-Si) wafer solar cells are 180 - 300 micrometers thick. Incident light is not fully absorbed in such thin-film layers, resulting in lower energy conversion efficiency compared to c-Si wafer solar cells. Therefore, effective light trapping is required to realise commercially-viable thin film cells, particularly for indirect-band-gap semiconductors such as crystalline silicon. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase cell photocurrent in many types of solar cells. This thesis presents the author s results on plasmonic polycrystalline silicon (poly-Si) thin film solar cells. It can be categorised into three parts, which are the optimum cell s surface condition for nanoparticle (NP) fabrication, optimisation of Ag NP fabrication process to enhance energy conversion efficiency and a wet-etching method for re-using metallised polycrystalline silicon thin film solar cells after NP deposition. The first part (Chapter 3.2) introduces the optimum surface condition for silver NPs. NPs are formed on Si film, a native SiO2 and a thermal SiO2 layer, and absorption, scattering cross section and potential short-circuit current density are compared for varying surface conditions. The sample with NPs on the thermal SiO2 layer shows better absorption at 500 700 nm wavelength range, whilst the sample with NPs on the native SiO2 and with NPs directly on Si show higher absorption at greater than 700 nm. The sample with NPs on the native SiO2 layer indicates 62.5% potential short circuit current density enhancement, which is 0.7% and 12% higher enhancement than that of the sample with NPs directly on Si and NPs on the thermal SiO2 layer, respectively. The second part (Chapter 3.3) is a systematic study of optimisation of Ag NP fabrication process for enhancing efficiency of poly-Si thin film solar cells. Three factors are studied: the Ag precursor film thickness, annealing temperature and time. The thickness of the precursor film was 10, 14 and 20 nm; annealing temperature was 190, 200, 230 and 260°C; and annealing time was varied between 20 to 95 min. NPs formed from 14 nm thick Ag precursor film annealed at 230°C for 53 min result in the highest photocurrent enhancement, 33.5%, efficiency enhancement 32% and the plasmonic cell efficiency of 5.32% without a back reflector and 5.95% with the back reflector which is the highest reported efficiency for plasmonic poly-Si thin film solar cells. The last part (Chapter 3.4) introduces a wet-etching-based method for re-using metallised poly-Si thin film solar cells after NP deposition. Nitric acid is used to etch Ag NPs on the metallised cells. The optical and electrical properties of the metallised cell are compared before and after etching. The optical and electrical properties of the cell after etching are well matched with the initial value, and the Si film and the aluminium contacts are not damaged by the etching solution even after five times etching

Study on Mitigation Method of Solder Corrosion for Crystalline Silicon Photovoltaic Modules

The corrosion of 62Sn36Pb2Ag solder connections poses serious difficulties for outdoor-exposed photovoltaic (PV) modules, as connection degradation contributes to the increase in series resistance (RS) of PV modules. In this study, we investigated a corrosion mitigation method based on the corrosion mechanism. The effect of added sacrificial metal on the reliability of PV modules was evaluated using the oxidation-reduction (redox) reaction under damp heat (DH) conditions. Experimental results after exposure to DH show that the main reason for the decrease in power was a drop in the module’s fill factor. This drop was attributed to the increase of RS. The drop in output power of the PV module without added sacrificial metal is greater than that of the sample with sacrificial metal. Electroluminescence and current-voltage mapping analysis also show that the PV module with sacrificial metal experienced less degradation than the sample without sacrificial metal

Conditions for the differentiation of melanocyte-precursor cells from human cord blood-derived mesenchymal stem cells

The loss of skin pigmentation can induce compromised cutaneous immunity, which can result in conditions such as vitiligo. In this study, we evaluated various agents that are able to induce the differentiation of stem cells into melanocytes. We found that a mixture of forskolin (FK), stem cell factor (SCF) and endothelin-3 (EDN-3) induced melanocyte-like morphology in human cord blood-derived mesenchymal stem cells (CB-MSCs). In addition, significant expression of microphthalmia-associated transcription factor-M and tyrosinase-related protein-1 genes was observed. These results suggest that a mixture of FK, SCF and EDN-3 induces the differentiation of melanocyte-precursor cells (MPCs) from CB-MSCs.Keywords: mesenchymal stem cells, melanocyte-precursor cells, forskolin, microphthalmia-associated transcription factor-M, tyrosinase-related protein-1African Journal of Biotechnology Vol. 9(36), pp. 5975-5977, 6 September, 201

Exact Algorithm for the Capacitated Team Orienteering Problem with Time Windows

The capacitated team orienteering problem with time windows (CTOPTW) is a problem to determine players' paths that have the maximum rewards while satisfying the constraints. In this paper, we present the exact solution approach for the CTOPTW which has not been done in previous literature. We show that the branch-and-price (B&P) scheme which was originally developed for the team orienteering problem can be applied to the CTOPTW. To solve pricing problems, we used implicit enumeration acceleration techniques, heuristic algorithms, and ng-route relaxations

Spermidine-induced recovery of human dermal structure and barrier function by skin microbiome.

An unbalanced microbial ecosystem on the human skin is closely related to skin diseases and has been associated with inflammation and immune responses. However, little is known about the role of the skin microbiome on skin aging. Here, we report that the Streptococcus species improved the skin structure and barrier function, thereby contributing to anti-aging. Metagenomic analyses showed the abundance of Streptococcus in younger individuals or those having more elastic skin. Particularly, we isolated Streptococcus pneumoniae, Streptococcus infantis, and Streptococcus thermophilus from face of young individuals. Treatment with secretions of S. pneumoniae and S. infantis induced the expression of genes associated with the formation of skin structure and the skin barrier function in human skin cells. The application of culture supernatant including Streptococcal secretions on human skin showed marked improvements on skin phenotypes such as elasticity, hydration, and desquamation. Gene Ontology analysis revealed overlaps in spermidine biosynthetic and glycogen biosynthetic processes. Streptococcus-secreted spermidine contributed to the recovery of skin structure and barrier function through the upregulation of collagen and lipid synthesis in aged cells. Overall, our data suggest the role of skin microbiome into anti-aging and clinical applications

Population pharmacokinetics of everolimus in patients with seizures associated with focal cortical dysplasia

Background: Everolimus is an inhibitor of mammalian target of rapamycin complex 1. As mutations in TSC1 and TSC2, which cause partial-onset seizures associated with TSC, were found in focal cortical dysplasia type Ⅱ (FCD Ⅱ) patients, a clinical trial has been performed to explore the efficacy and safety of everolimus in FCD patients. However, no dosage regimen was determined to treat FCD II. To recommend an optimal dose regimen for FCD patients, a population pharmacokinetic model of everolimus in FCD patients was developed.Methods: The data of everolimus were collected from September 2017 to May 2020 in a tertiary-level hospital in Korea. The model was developed using NONMEM® software version 7.4.1 (Icon Development Solutions, Ellicott City, MD, United States).Results: The population pharmacokinetics of everolimus was described as the one-compartment model with first-order absorption, with the effect of BSA on clearance. The final model was built as follows: TVCL = 12.5 + 9.71 × (BSA/1.5), TVV = 293, and TVKA = 0.585. As a result of simulation, a dose higher than 7 mg/m2 is needed in patients with BSA 0.5 m2, and a dose higher than 6 mg/m2 is needed in patients with BSA 0.7 m2. A dose of 4.5 mg/m2 is enough in the population with BSA higher than 1.5 m2 to meet the target trough range of 5–15 ng/mL.Conclusion: Based on the developed pharmacokinetics model, the optimal dose of everolimus in practice was recommended by considering the available strengths of Afinitor disperz®, 2 mg, 3 mg, and 5 mg