Exploiting extrinsic passivation on thin film dielectrics for high efficiency silicon solar cells

Lead Research Organisation: University of Oxford
Department Name: Materials

Abstract

The aim of this project is to develop methods of extrinsic surface passivation to produce high-performing crystalline silicon solar cells. The efficiency of solar cells is largely limited by the recombination of electrons and holes at surfaces and interfaces, where there is a high concentration of material defects. Future generations of industrial solar cells will require cost effective techniques for producing semiconductor-dielectric interfaces with very low rates of recombination.

Therefore, this project will focus on advancing both chemical and field effect passivation techniques to decrease charge recombination losses at surface and interface sites. Such techniques will consist of dielectric, hydrogen and ionic passivation methods, with an emphasis on long-term durability and industrial compatibility. Improved silicon surfaces will be achieved through the chemical removal of defect sites and the stabilisation of extrinsic ionic charges. As a means of achieving the objective, a study of the optimal deposition and processing techniques will be carried out.

EPSRC theme: Energy

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1922038 Studentship EP/N509711/1 01/10/2017 31/03/2021 Isabel Al-Dhahir
 
Description One important aspect of my research has been to demonstrate the ability to control the chemical passivation of a silicon/silicon oxide interface using a surface electric field. My results have shown this is indeed possible. I hypothesise that changes in chemical passivation vary under an electric field due to the response of charged hydrogen atoms within the dielectric to the polarity of the field. More work is needed to confirm the involvement of hydrogen specifically.

A second component to my work is migrating positive ions to the silicon/silicon oxide interface as stable charges. In general, the placement of such ions are proven to influence the electron and hole carrier concentrations at that interface. Positive ions repel holes away from the interface, and therefore reduce recombination between the electrons and holes which improves the efficiency of the cell. However, certain ions are less stable than others and migrating too many across to the interface can have a detrimental effect on the quality. I am studying a range of ions and processing methods that have not been demonstrated before and testing for their stability and improvement on the silicon's passivation.
Exploitation Route To future researchers, this project will provide a thorough understanding of new methods to reduce defects on the silicon surface. Additionally, the areas studied in this project are industrially relevant and could influence the manufacture of commercial solar panels.
Sectors Energy