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Carrier Collection Process in InGaAs/GaAs Superlattice Structured Solar Cells
S. Yagi, S. Nagamochi, R. Oshima, Y. Okada
III-V Semiconductor, Quantum Well, Solar Cell
Advanced Photovoltaics
Subtopic: Fundamental Studies
Event: 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session: 1AO.4.5
45 - 48
ISBN: 3-936338-24-8
Paper DOI: 10.4229/23rdEUPVSEC2008-1AO.4.5
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Document(s): paper


The effect of carrier transport via tunneling on the carrier collection process in multi-quantum well (MQW) solar cells was studied. Dependence of photocurrent and photoluminescence on the thickness of barrier layers in InGaAs/GaAs MQW solar cells were investigated. We show that the escape of photocarriers from MQWs and hence, suppression of radiative recombination are promoted with decreasing thickness of GaAs barriers. For MQW cells with GaAs barrier thickness of <10 nm, photocarriers can tunnel through the miniband, and consequently the activation energy of carrier escape from quantum wells is reduced due to acceleration of photocarriers by the electric field. A fast spatial separation of electron-hole pairs and enhancement of carrier escape result in a rapid quenching of PL emission and efficient carrier collection even at low temperatures. This result verifies that the enhancement of carrier collection is as a result of formation of superlattice minibands in periodic nanostructures, and is an important observation in order to achieve high efficiencies in nanostructured solar cells using QWs and quantum dots (QDs).