Browsing by Author "Phillips, Jamie"

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Decoupling Spectral Overlap of Intermediate Band Solar Cells using Low-High State Filling
(2012)
Lin, Albert
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Phillips, Jamie
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The high efficiency predicted for solar cells based on multi-photon processes relies on the assumption of optical transitions with non-overlapping spectral bands. Spectral overlap reduces the conversion efficiency due to energy loss associated with improper usage of higher energy photons for lower energy optical transitions. In this study, device structures with non-uniform occupation of intermediate electronic states are proposed to reduce the dependence of conversion efficiency on spectral overlap. Solar cell conversion efficiencies are calculated for structures where absorption bands are spatially decoupled due to defined occupation of intermediate states. Conversion efficiencies for a two section and three section device with spectral overlap of 4 eV are determined to be 52.8 % and 61.5 %, respectively, and are significantly larger than the calculated efficiency of 35.1% for the case of a standard multi-photon cell with uniform half-filled intermediate states The spectrally-decoupled device provides a means to achieve high theoretical efficiency independent of spectral overlap that approaches the detailed balance efficiency limit of 63.2 % for intermediate state devices without spectral overlap and 63.8 % for unconstrained triple-junction tandem cells.
Resolving spectral overlap issue of intermediate band solar cells using non-uniform sub-bandgap state filling
(2014-10-01)
Lin, Albert
;
Phillips, Jamie
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交大名義發表
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電子工程學系及電子研究所
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National Chiao Tung University
Intermediate band solar cell provides novel alternative to multi-junction solar cell, but its efficiency is significantly degraded when spectral overlap exists between different absorption bands. Here, a scheme using non-uniform sub-bandgap state filling together with intermediate band transport is proposed to resolve the spectral overlap issue. On the basis of detailed balance calculation, spectrally decoupled devices using low-high state filling is shown to achieve 52.8% conversion efficiency when 4eV spectral overlap is present between absorption coefficients of different bands, compared with baseline efficiency equal to 35.1% for conventional half-filled intermediate band devices. If a base material without intermediate band is added to the two section low-high state filling devices, the efficiency is further increased to 61.5%, which approaches efficiency of 63.2% for intermediate band devices with no spectral overlap and 63.8% for unconstrained triple-junction tandem cells. The junction thermalization loss associated with proposed new structures is shown to be equal to conventional half-filled intermediate band devices. Copyright (c) 2013 John Wiley & Sons, Ltd.