The demonstration of a highly efficient SiGe Type-II hetero-junction solar cell with an optimal stress design
Journal
Thin Solid Films
Journal Volume
544
Pages
112-115
Date Issued
2013
Author(s)
Abstract
Highly efficient surface-textured SiGe-based solar cell with top surface trench structure and optimized SiGe/Si type-II hetero-junction design is proposed. The surface-textured structure results in a significant reduction of the surface reflectance from 32% to ~10% in the visible light region with an obvious photonic crystal effect, which can be simulated by finite differential time domain calculations. By varying the top surface trench spacing, broadband antireflection can be realized and total absorption rate greatly enhanced. Moreover, SiGe/Si hetero-structure substrate has also been implemented to enhance the solar cell efficiency by an additional 3% in this work, not only due to the originally higher absorption rate in the SiGe-based material but also due to the enhanced SiGe/Si type-II hetero-structure substrate design. The offset and discontinuousness of the energy band between the Si substrate and the strained Si0.9Ge0.1 type-II hetero-junction structure resulted in higher local electron-hole carrier concentration, which is confined in the Si cap and SiGe quantum well structure, and the longer non-radiative Auger carrier recombination lifetime as measured by femtosecond transient absorption measurements. The integration of these two key technologies-nano- level surface trench structure and optimization of the SiGe/Si type-II hetero-structure, led to highly efficient (~18% for the stable production and 21% for the peak record) nano-surface textured SiGe-based solar cell being achieved and demonstrated in this work. © 2013 Published by Elsevier B.V.
SDGs
Type
journal article