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Published on: July 2, 2012
Photonic crystal intermediate reflectors for micromorph solar cells: a comparative study
P G O'Brien1, A Chutinan, K Leong
1Department of Materials Science and Engineering, University of Toronto, 184 College Street, room 140 Toronto, Ontario M5S 3E4, Canada.
Optics Express
|April 15, 2010
Summary
Bragg-reflectors enhance micromorph solar cell performance by increasing current in the upper amorphous silicon (a-Si:H) cell by up to 20%. This advanced reflector also boosts bottom microcrystalline silicon (μc-Si:H) cell current, outperforming ZnO opals.
Area of Science:
- Photovoltaics
- Materials Science
- Optics
Background:
- Micromorph solar cells combine amorphous silicon (a-Si:H) and microcrystalline silicon (μc-Si:H) for enhanced light absorption.
- Intermediate reflectors are crucial for optimizing light management and current generation in tandem solar cells.
Purpose of the Study:
- To investigate the effectiveness of Bragg-reflectors and inverted zinc oxide (ZnO) opals as intermediate reflectors in micromorph solar cells.
- To quantify the impact of these reflectors on current generation in both the upper a-Si:H and bottom μc-Si:H subcells.
Main Methods:
- Wave-optics analysis was employed to model light propagation and absorption within the micromorph cell structure.
- Performance metrics, specifically current generation, were calculated for cells with different intermediate reflector materials.
Main Results:
- Bragg-reflectors increased current in the 100 nm a-Si:H cell by up to 20%, while inverted ZnO opals yielded a 13% increase.
- The Bragg-reflector also improved current generation in the bottom μc-Si:H cell compared to the ZnO opal.
- Bragg-reflectors outperformed ZnO opals due to a larger stop-gap, optical thinness, and reduced absorption losses.
Conclusions:
- Bragg-reflectors are a superior choice for intermediate reflectors in micromorph solar cells compared to inverted ZnO opals.
- Optimized light management using Bragg-reflectors can significantly enhance the overall efficiency of micromorph photovoltaic devices.
