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Title:
 
Vertical Junction Si Micro-Cells for Concentrating Photovoltaics
 
Author(s):
 
R. Sarfaty, A. Cherkun, R. Pozner, G. Segev, E. Zeierman, Y. Flitsanov, A. Kribus, Y. Rosenwaks
 
Keywords:
 
Series Resistance, Concentrator PV, Vertical Multijunction, CPV Cell, High Voltage Cell
 
Topic:
 
Advanced Photovoltaics : New Concepts and Ultra-High Efficiency
Subtopic: Terrestrial Concentrator Systems
Event: 26th European Photovoltaic Solar Energy Conference and Exhibition
Session: 1BO.11.4
 
Pages:
 
145 - 147
ISBN: 3-936338-27-2
Paper DOI: 10.4229/26thEUPVSEC2011-1BO.11.4
 
Price:
 
 
0,00 EUR
 
Document(s): paper
 

Abstract/Summary:


Vertical Junction (VJ) silicon cells have shown potential to operate under high concentration due to low current/high voltage operation leading to lower series resistance losses, but tests have shown so far only modest efficiency of about 20%. We perform a comprehensive 2D and 3D optimization study and show that the efficiency of VMJ cells can be significantly higher, around 30% at concentration of 1000 and higher. Reaching high efficiency requires micro junction width of about 50 microns, which is significantly smaller than previous VMJ cells. This requires a monolithic approach to the fabrication process. We have realized separated vertical junctions with different widths on a SOI wafer. Efficiency characteristic of the VJ as a function of illumination intensity for various VJ widths behave as predicted by the simulation: highest efficiencies have been obtained by micro-VJ of 50 microns width. A 3D VJ structure based on pre-patterned macro-pores is also presented and analyzed. This structure approaches a back contact cell when the pore depth approaches zero. Simulation results show efficiency improvement with increasing pore depth, until the pores almost reach the upper surface. The predicted conversion efficiency at 1000 suns is also about 30%, significantly higher than conventional cells and previously reported VMJ cells.