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- Title
Absorption threshold extended to 1.15 eV using InGaAs/GaAsP quantum wells for over-50%-efficient lattice-matched quad-junction solar cells.
- Authors
Toprasertpong, Kasidit; Fujii, Hiromasa; Thomas, Tomos; Führer, Markus; Alonso‐Álvarez, Diego; Farrell, Daniel J.; Watanabe, Kentaroh; Okada, Yoshitaka; Ekins‐Daukes, Nicholas J.; Sugiyama, Masakazu; Nakano, Yoshiaki
- Abstract
Bandgap engineering of strain-balanced InGaAs/GaAsP multiple quantum wells (MQWs) allows high-quality materials with an absorption edge beyond GaAs to be epitaxially grown in Ge/GaAs-based multijunction solar cells. We demonstrate MQW solar cells with effective bandgaps ranging from 1.31 eV to as low as 1.15 eV. The bandgap-voltage-offset of MQWs is found to be independent of effective bandgaps and superior to a bulk reference by approximately 0.1 V. This implies the merit of high photovoltage as compared with bulk cells with the same bandgap in addition to their widely bandgap-tunable property. Towards the realization of fully lattice-matched quad-junction devices, we demonstrate a 70-period, 1.15-eV bandgap MQW cell as a promising material in 0.66/1.15/1.51/1.99-eV quad-junction cells, whose practical efficiency has a potential to achieve over 50%. With such a large period number of MQWs, the reverse-biased external quantum efficiency reaches an average of over 60% in the spectral region corresponding to a 1.15-eV subcell; this is achieved with only a-few-percent drop at short-circuit condition. The device presented here reaches the target open-circuit voltage and over 75% of the current density required for realizing a 1.15-eV subcell in a 50%-efficient quad-junction solar cell. We believe that future devices which exploit light-trapping structures and enhanced carrier extraction will be able to reach the desired target. Copyright © 2015 John Wiley & Sons, Ltd.
- Subjects
QUANTUM wells; ABSORPTION; SOLAR cells; SEMICONDUCTOR research; GALLIUM arsenide
- Publication
Progress in Photovoltaics, 2016, Vol 24, Issue 4, p533
- ISSN
1062-7995
- Publication type
Article
- DOI
10.1002/pip.2585