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Projects: Projects for Investigator
Reference Number EP/H019987/1
Title Elimination of Efficiency Degradation Mechanisms in Silicon Photovoltaic Solar Cells
Status Completed
Energy Categories Renewable Energy Sources(Solar Energy, Photovoltaics) 100%;
Research Types Basic and strategic applied research 100%
Science and Technology Fields PHYSICAL SCIENCES AND MATHEMATICS (Chemistry) 50%;
ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 50%;
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Professor B Hamilton
No email address given
Physics and Astronomy
University of Manchester
Award Type Standard
Funding Source EPSRC
Start Date 01 February 2010
End Date 31 July 2012
Duration 30 months
Total Grant Value £268,035
Industrial Sectors Energy
Region North West
Programme Energy : Physical Sciences
Investigators Principal Investigator Professor B Hamilton , Physics and Astronomy, University of Manchester (99.999%)
  Other Investigator Professor AR Peaker , Electrical & Electronic Engineering, University of Manchester (0.001%)
  Industrial Collaborator Project Contact , MEMC Electronic Materials SpA, Italy (0.000%)
Project Contact , Universidade de Aveiro, Portugal (0.000%)
Project Contact , Solar Energy Research GmbH Hameln / Emmerthal (ISFH), Germany (0.000%)
Web Site
Abstract Photovoltaic Solar Cells seem certain to make a significant contribution to the world's energy needs in the 21st Century. At the present time such devices only convert a small part of the 1kW per square meter of radiation from the sun which falls on the earth's surface into electricity. Typical commercial silicon devices that use un-concentrated sunlight are less than 15% efficient although laboratory devices with efficiencies as high as 24% have been made. Many very interesting ideas have been put forward for higher efficiency 3rd generation cells but most of these are a very long way from commercial realization on a large economic scale. At the present time 90% of production is based on wafered silicon (Czochralski single crystal or cast poly-crystalline). The predicted production for 2010 using existing silicon technology will have a peak output of 26GW.Unfortunately in their initial few hours of operation most silicon solar cells suffer from degradation which stabilizes after a reduction in efficiency of 10% relative ie a 20% cell becomes an 18% cell. In the context of total photovoltaic power lost on a world scale this is very significant. It is believed that the reduction in efficiency is due to a defect reaction in the silicon in which oxygen dimers diffuse to the boron dopant to form a powerful recombination centre. The problem is not restricted to the commercial devices of the next decade but is also highly relevant to some ofthe most promising third generation (high efficiency) cells which use silicon as part of the active structure. This research proposal aims to eliminate the degradation process by removing the reaction path from the silicon prior to the formation of the recombination centre. An essential pre-requisite to this is to achieve a detailed understanding of the defect centres and their formation.We have previously studied the oxygen dimers which are currently thought to be the precursors of the recombination centre. These can be detected using optical absorption measurements, ideally at low temperatures (~10K). Preliminary work indicates that it should be possible to develop treatments of the silicon material which reduce the concentration of the dimers to a negligible level in the finished cell and, because the dimers do not form at normal operating temperatures, so eliminate the formation of the defect. It would be quite feasible using this approach to maintain the concentration ofinterstitial oxygen which provides mechanical strength to the silicon with consequent yield and cost benefits. In this work the recombination centre will be studied using minority carrier Laplace Deep Level Spectroscopy and its structure determined by the application of uniaxial stress. The reaction of the oxygen dimer will be studied as the recombination centre forms, in real time, using optical absorption techniques. The work will be done in collaboration with MEMC who are one of the leadingmanufactures of solar silicon, the Institut fr Solarenergieforschung Hameln/Emmerthal (ISFH) in Germany who have undertaken much experimental work recently on solar cell degradation and the University of Aveiro in Portugal who will collaborate on theoretical calculations to support the Manchester work
Publications (none)
Final Report (none)
Added to Database 23/12/09