Presentation Details
| Thermal Stress Behavior of Thin-Film III-V Tandem Solar Cells (yes) Jenny Norberg1, 2, Joachim Herderich1, 2, Alessandra Selis1, Henning Helmers1, Oliver Höhn1, 2. 1Fraunhofer Institute for Solar Energy Systems ISE, Freiburg im Breisgau, Germany.2University of Freiburg, Freiburg im Breisgau, Germany |
Abstract
Thin-film III-V tandem solar cells promise high efficiencies while reducing semiconductor material consumption by detaching the active layers from the growth substrate. The resulting device is only a few micrometers thick and stabilized with a flexible holder on the rear side. A multilayer stack in this thickness range creates new challenges because of thermal residual stresses forming in each layer. This work investigates the thermal stress behavior of thin-film tandem devices exposed to thermal cycling. An analytical model is developed to predict residual stress evolution within the multilayer stack. The model is calibrated using wafer curvature measurements of each constituent material. Different rear side designs are studied to assess their impact on stress distribution in the active region – a major cause for cracking of the III-V material. The performance of two thin-film GaInP/GaAs tandem solar cells with different rear-side layer stacks is compared. The champion device has a total device thickness of 15 µm (excluding front contacts) and achieves an efficiency of 30.9 %, resulting in a specific power of 2.3 kW/kg.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.