Details of Grant 

EPSRC Reference:	GR/J83529/01
Title:	THE PHYSICS OF QUANTUM WELL SOLAR CELLS (QWSC)
Principal Investigator:	Barnham, Professor K
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Physics
Organisation:	Imperial College London
Scheme:	Standard Research (Pre-FEC)
Starts:	01 June 1994	Ends:	31 May 1997	Value (£):	200,002
EPSRC Research Topic Classifications:	Energy Efficiency Optoelect. Devices & Circuits Solar Technology
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
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Panel History:
Summary on Grant Application Form
The group has pioneered the study of a novel solar cell, the Quantum Well Solar Cell (QWSC), which has the potential to achieve higher power conversion efficiency. It also has particular advantages for the light-concentration systems which can help reduce considerably the costs of solar electricity.Progress:The QWSC is the first use in solar cells of the quantum well (QW) techniques which have been extensively studied for information technology applications, for example in lasers and optical modulators. Our study is the first systematic investigation of multi-quantum well systems in the situation where power is extracted from the wells. The physics is interesting but the material quality constraints are quite strong.We have already demonstrated that QWs enhance short-circuit current compared to a conventional solar cell made from the barrier material. We have shown that we can dramatically enhance the efficiency of relatively poor AlGaAs conventional p-i-n solar cells by adding 30-50 wells in the intrinsic region.Much of our research effort has gone into understanding the complex questions of carrier escape from the wells in forward bias and the voltage dependence of the AlGaAs/GaAs QWSC (Grant GR/J83529) and in extending our studies to material systems with the potential to achieve higher efficiency (Grant GR/H44868). Recently, we have made important progress by demonstrating, in three material systems, that QWs enhance open-circuit voltage compared to conventional cells made from the well material. A QWSC based on the GaAs conventional cell offers the prospect of achieving the highest efficiencies. However the strained InGaAs QWs system makes for additional material quality problems which limit the number and depth of the wells which can be incorporated. By studying both MOVPE and MBE grown material we have shown that a short-circuit current enhancement can be achieved which compensates for the loss of voltage in comparison with a high efficiency GaAs cell. We have also shown that a rear surface mirror can more than double the absorption of in the wells without detriment to the voltage performance on small photodiode devices. One immediate objective now is to achieve the same effect with a mirror on a larger, solar cell compatible, device and so achieve efficiency enhancement in a high-efficiency cell.
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Organisation Website:	http://www.imperial.ac.uk