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Realization of Significant Absorption Enhancement in Thin Film Silicon Solar Cells with Textured Photonic Crystal Backside Reflector

Published online by Cambridge University Press:  21 March 2011

Lirong Zeng
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Peter Bermel
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Yasha Yi
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Bernard A. Alamariu
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Kurt A. Broderick
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Jifeng Liu
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Ching-yin Hong
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Xiaoman Duan
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
John Joannopoulos
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
Lionel C. Kimerling
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA, 02139
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Abstract

The major factor limiting the efficiencies of thin film Si solar cells is their weak absorption of red and near-infrared photons due to short optical path length and indirect bandgap. Powerful light trapping is essential to confine light inside the cell for sufficient absorption. Here we report the first experimental application of a new light trapping scheme, the textured photonic crystal (TPC) backside reflector, to monocrystalline thin film Si solar cells. TPC combines a onedimensional photonic crystal, i.e., a distributed Bragg reflector (DBR), with a reflection grating. The near unity reflectivity of DBR in a wide omnidirectional bandgap and the large angle diffraction by the grating ensures a strong enhancement in the absorption of red and near-infrared photons, leading to significant improvements in cell efficiencies. Measured short circuit current density Jsc was increased by 19% for 5 μm thick cells, and 11% for 20 μm thick cells, compared to theoretical predictions of 28% and 14%, respectively.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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