Improved efficiency of microcrystalline silicon thin film solar cells with wide band-gap CdS buffer layer

In this paper, we have reported a new structure based upon an optical simulation of maximum light trapping and management in microcrystalline silicon thin film solar cells by using multi texture schemes and introducing an n-type cadmium sulphide (CdS) buffer layer with the goal of extreme light coupling and absorption in silicon absorber layer. Photon absorption was improved by optimising the front and back texturing of transparent conductive oxide (TCO) layers and variation in buffer layer thickness. We have demonstrated that light trapping can be improved with proposed geometry of 1μm thick crystalline silicon absorber layer below a thin layer of wide band gap material. We have improved the short circuit current densities by 1.35mA/cm2 resulting in a total short circuit current of 25 mA/cm2 and conversion efficiency of 9% with the addition of CdS buffer layer and multi textures, under global AM1.5 conditions. In this study, we have used 2 Dimensional Full Vectorial Finite Element (2DFVFEM) to design and optimize the proposed light propagation in solar cell structure configuration. Our simulation results show that interface morphology of CdS layer thickness and textures with different aspect and ratios have the most prominent influence on solar cell performance in terms of both short circuit current and quantum efficiency

Modelling Changing Hospital Service Accessibility in Ireland 1999-2006

On the island of Ireland, there are two distinct and separate jurisdictions, namely the Republic of Ireland and Northern Ireland. Both were founded in 1922 with the former developing into an independent state while the latter still remains a part of the United Kingdom. The Irish Republic operates a primarily state-funded health care system, but an increasing input from private health insurance has arguably created a two-tier publicprivate system (Wren 2003). Northern Ireland’s health care system is primarily based on the UK’s National Health System (NHS) with some place-based variation (Jordan et. al. 2006). With the recent peace in Northern Ireland and the success of the ‘Celtic Tiger’ economy of the South, both governments are exploring joining up the economic and social structures across the whole island. Modelling access to health is one of the areas, which are currently being explored. Informally, there has been cross-border movement in the utilisation of health care for decades but there has been no strategic approach to modeling the implications of those flows. The need to plan in a cross-border setting is also explicitly stated in the new Republic of Ireland National Development Plan (NDP) for the period 2007-2013. With both governments being engaged in the restructuring of health care services, the Departments of Health in both countries were keen to explore the spatial dimension. As a result the potential of a GIS-based approach was identified as worthy of exploration. The National Centre for GeoComputation (NCG) at NUI Maynooth were approached and asked to develop an initial modelling of access to hospitals on an All-Ireland basis. A number of problems needed to be addressed related to the compatibility of spatial data, data merging in a cross-border environment and reliability issues. However each of these issues were likely to be an issue affecting the quality of the GIS analysis. The combined datasets were then used to examine the potential impact of policy-driven change both north and south of the border

Modeling the effect of predicted sea-level rise on coastal conservation habitats using GIS

Global average temperatures have in creased by about 0.6°C (± 0.2°C) during the 20th century, and are project ed to increase by 1.4 - 5.8°C by 2100 (IPCC, 2001a). The relationship between atmospheric warming and sea-level rise (SLR) is well understood, and this change is predicted to lead to SLR of up to 1m by 2100, cr eating consequences for coastal communities and environments worldwide (IPCC, 2001b)