Novel photovoltaic solar power generating diode

Banyamin, Ziad (2014) Novel photovoltaic solar power generating diode. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Thin film solar cells are based on semiconductor materials which are configured together to form a single p-n junction. The p-n junction diode is effectively a simple device that has the capacity to absorb part of the sunlight spectrum and deliver the absorbed photon energy to carriers of electrical current known as electrons and holes. A simple p-n junction solar cell device consists of a p-n junction, a metallic grid and a back contact. The aim of this project was to develop and fabricate a p-n heterojunction diode that is robust, developed with low cost and suitable for large surface area. The device attains a heterojunction configuration, consisting of two thin films, each exhibiting different semiconducting behaviour, namely n-type and p-type semiconductors that are brought together to form a p-n junction diode device. The initial stage of this research was to make and characterise a range of oxide coating compositions that can be sputtered from blends of loosely packed powder targets, using the pulsed DC magnetron sputtering technique. These compositions include fluorine doped tin oxide, antimony doped tin oxide and titanium oxide. The different coatings should be transparent conductive oxides (TCO) that exhibit an n-type semiconductor material characteristic. The second objective was to characterise and develop a p-type semiconductor namely copper aluminium oxide to investigate the optimum compositional ratio and the effect of deposition power on the structure of the thin films. The thin films were characterised in terms of their structural, morphological, optical (transmission and band-gap) and electrical (resistivity, mobility and carrier concentration) conditions. The collection of the charge carriers generated from the incident light was achieved through metal ohmic contacts. This was deposited onto both sides of the device using copper and the silver grids/contacts that are deposited onto the n-type layer and the p-type layers, respectively. The design layout of the grid was optimised in order to increase the device efficiency. The final part of this project was to construct the p-n junction device, test the electrical (current-voltage characteristics) performance and investigate the rectifying behaviour and the formation of the p-n junction.