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Impact of Photon Recycling and Luminescence Coupling in III-V Photovoltaic Devices

: Walker, A.; Höhn, O.; Micha, D.; Wagner, L.; Helmers, H.; Dimroth, F.; Bett, A.


Freundlich, A. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV : San Francisco, California, United States | February 7, 2015
Bellingham, WA: SPIE, 2015 (SPIE Proceedings 9358)
ISBN: 978-1-62841-448-6
Art. 93580A
Photonics West Conference <2015, San Francisco/Calif.>
Conference Paper
Fraunhofer ISE ()
Solarzelle; Technologie; III-V und Konzentrator-Photovoltaik; III-V Epitaxie und Solarzellen; recycling; semiconductor; simulation; Materialien - Solarzellen und Technologie

ingle junction photovoltaic devices composed of direct bandgap III-V semiconductors such as GaAs can exploit the effects of photon recycling to achieve record-high open circuit voltages. Modeling such devices yields insight into the design and material criteria required to achieve high efficiencies. For a GaAs cell to reach 28 % efficiency without a substrate, the Shockley-Read-Hall (SRH) lifetimes of the electrons and holes must be longer than 3 s and 100 ns respectively in a 2 μm thin active region coupled to a very high reflective (>99%) rear-side mirror. The model is generalized to account for luminescence coupling in tandem devices, which yields direct insight into the top cell’s non-radiative lifetimes. A heavily current mismatched GaAs/GaAs tandem device is simulated and measured experimentally as a function of concentration between 3 and 100 suns. The luminescence coupling increases from 14 % to 33 % experimentally, whereas the model requires an increasing SRH lifetime for both electrons and holes to explain these experimental results. However, intermediate absorbing GaAs layers between the two sub-cells may also increasingly contribute to the luminescence coupling as a function of concentration.