Presentation Details
| Supressing Sub-Bandgap Luminescence from CdSe Films Kiran Lamichhane, Tyler Brau, Adam B.Phillips, Manoj K.Jamarkattel, Ebin Bastola, Isuru Lakmal, Kara B.Kile, Prabodika N.Kaluarachchi, Zulkifl Hussain, Arun Basnet, Sabin Neupane, Ujjwal Dhakal, Sanjeeb Budhathoki, Abasi Abudulimu, Yanfa Yan, Randy J.Ellingson, Michael J.Heben. Wright Center for Photovoltaic Innovation and Commercialization, Department of Physics and Astronomy, Toledo, OH, USA |
Abstract
Sub-bandgap defects in CdSe limit the attainable open circuit voltage of the devices, thereby limiting overall performance. Consequently, suppression of these defect states is necessary for CdSe to be a viable top cell in tandem devices. To address this, we processed CdSe films under numerous controlled conditions. Oxygen-free CdCl2 heat treatment (CHT) led to grain growth and strong band edge photoluminescence response with no long wavelength (> 800 nm) response. On the other hand, samples that underwent CHT in dry air demonstrated lower band edge emission with significant long wavelength response. In addition, oxygen-free CHT incorporating eutectics with CdCl2 and NaCl or KCl showed enhanced grain growth compared to neat CdCl2, although their band edge emission intensity remained comparable. These results suggest that presence of oxygen during the CHT is critical to both sub-bandgap emission processes, which are attributed to poor device performance. The results presented here strongly suggest pathways to suppress the sub-bandgap luminescence of CdSe films, potentially enabling high efficiency devices.
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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.