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Title:
 
High Efficiency Si Solar Cells with Photonic Crystal Rear Reflector
 
Author(s):
 
B.G. Lee, J. Eisenlohr, F. Feldmann, M. Drießen, T. Rachow, N. Tucher, J.C. Goldschmidt, J. Benick, M. Hermle
 
Keywords:
 
Light Trapping, Silicon Solar Cell(s), Photonic Crystal
 
Topic:
 
WAFER-BASED SILICON SOLAR CELLS AND MATERIALS TECHNOLOGY
Subtopic: Silicon Solar Cell Improvements
Event: 31st European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AV.2.6
 
Pages:
 
642 - 644
ISBN: 3-936338-39-6
Paper DOI: 10.4229/EUPVSEC20152015-2AV.2.6
 
Price:
 
 
0,00 EUR
 
Document(s): paper
 

Abstract/Summary:


A photonic crystal rear reflector is demonstrated to increase the photocurrent of high efficiency Si solar cells; specifically, a rear sphere grating structure is shown to improve the performance of a cell by enhancing its absorption of near-infrared photons. A cell with a planar front surface and rear sphere grating is fabricated and achieves 22.1% efficiency with a remarkably high short-circuit current density of 38.1 mA/cm2. Solar cell quantum efficiency (QE) measurements reveal an increase in photocurrent from longer-wavelength light near the bandgap of Si, as compared to the equivalent cell having a lossless flat mirror at the rear. This demonstrates the effectiveness of the rear sphere grating as a light-trapping structure that increases the optical path-length and absorption within the cell. Moreover, optical measurements indicate that a cell having a random pyramid texture on the front side and a rear sphere grating could almost reach the Yablonovitch limit calculated for light-trapping.