Clean Technology 2009

Quantum Tunneling Design for Efficient Carrier Collection in p-i-n III-V Quantum-Confined Solar Cells

A. Alemu, C. Karunaratne, G. Radhakrishnan, A. Freundlich
University of Houston, US

Keywords: tunneling, escape, solar cell, III-V, quantum confined


III-V semiconductor based quantum structures displaying quasi-3D holes and resonant tunneling alignment at the conduction band and incorporated in the intrinsic region of p-i-n GaAs solar cells are investigated. The choices of the material system and energy band design are tuned towards facilitating the collection of all photo-generated carriers while minimizing recombination losses. A k.p based band structure model including strain and spin orbit interactions complemented by a transfer matrix method is used for the analysis and optimization of the transport properties. Ultra-fast carrier transfer times in the order of 10^-15 s are obtained indicating the possibility of extracting carriers before slower recombination losses. In particular, the designs are expected to minimize radiative recombination usually occurring with much longer lifetimes (~ 10^-9 s). The faster spatial separation between tunneling electrons and quasi-3D holes under electric field is also expected to play a key role in reducing carrier recombination. Such carefully engineered quantum confined material system optimized for improved collection of photo-generated carriers is anticipated to usher conversion efficiencies in the vicinity of ideal limits.
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