Silicon Epitaxial Layers Grown on Buried Porous Silicon Templates for solar cells: Detailed Electrical and Chemical Understanding

Name: Hariharsudan Sivaramakrishnan Radhakrishnan

•   Prof. dr. ir. Robert Pierre Mertens (promotor)
•   Prof. dr. ir. Jozef Poortmans (co-promotor)

In order to place solar power prominently in the global energy mix in the long term future, there needs to be continued cost reductions in the photovoltaic industry. In silicon photovoltaics, which forms 85-90% of the market, the cost of the silicon material itself forms a major fraction of the final solar module cost. Thus, the international technology roadmap for photovoltaic (ITRPV) forecasts a continuous reduction in the thickness of the wafer used to fabricate the solar cells.
With reduction in consumption of high quality expensive silicon as the motivation, two silicon solar cell concepts have been envisaged, namely the wafer-equivalent epitaxial silicon solar cell (WE-epicell) and the layer-transferred epitaxial silicon solar cell (LT-epicell). In both cell concepts, theentire photovoltaic power conversion occurs in a thin (20-50 µm) epitaxially-grown layer. In comparison, the thickness of a standard silicon solar cell is ~170 µm.
In WE-epicells, the epitaxial layer is grown on a low-cost and often low-purity native multi-crystalline silicon substrate, on which it remains attached in the final solar cell. In LT-epicells, the epitaxial layer is grown on a high quality mono-crystalline silicon substrate and then transferred to a low-cost carrier such as glass. Inboth cell concepts, porous silicon plays important functions.
The work of this thesis focuses on the in-depth study of two of these functions: (1) porous silicon as a gettering layer in the context of WE-epicellsand (2) porous silicon as a template for epitaxial growth in the context of both WE-epicells and LT-epicells. Based on the theoretical and experimental understanding from these studies, suggestions for improvement of porous silicon as a gettering layer and as a template for epitaxy are proposed and implemented.

 

https://lirias.kuleuven.be/handle/123456789/441476

•   Prof. dr. ir. Robert Pierre Mertens (promotor)
•   Prof. dr. ir. Jozef Poortmans (co-promotor)
•   Prof. dr. ir. Paul Van Houtte (voorzitter/chairman)
•   Prof. dr. ir. Johan Driesen (secretaris/secretary)
•   Prof. dr. Marc Seefeldt
•   Dr. Frédéric Dross , Hanwha Solar America
•   Prof. dr. Nick E.B. Cowern , Newcastle University
•   Dr. Sarah Kajari-Schröder , ISFH