Presentation Details
| Nanoscale Investigation of Defects in CdCl2 Treated CdSe Thin Films Xiaolei Liu, Zhaoxia Zhou, Jacques Kenyon, Rob Ellis, Kerrie Morris, Zeyad Elsayed, Sam Machin, Kieran Curson, Jake Bowers, Michael Walls. Loughborough University, Loughborough, United Kingdom |
Abstract
CdSe is an ideal candidate for a top cell in a silicon based tandem photovoltaic (PV) device due to its bandgap of 1.7 eV. However, the PV research community has overlooked the potential of polycrystalline CdSe absorber because it has been thought to be “photo-inactive”. Recently, we discovered that the cadmium chloride activation treatment can make the CdSe highly photoactive in a CdSeTe/CdTe device, i.e. 5x more emissive than CdTe. In this work, we used photoluminescence and nanoscale cathodoluminescence (CL) to identify sub-bandgap emissions of defects–including Se vacancies, OSe antisite defects, and stacking faults– in CdCl2 treated CdSe thin films. The Se vacancies become more significant on grain boundaries compared to surrounding grain interiors. The CdCl2 treatment reduces the OSe antisite defects and passivates CdSe grain boundaries to reduce the recombination velocity. The high spatial resolution CL enables the observation of the defects and also provides precise identification of where they occur. By combining it with high resolution transmission electron microscopy, we can correlate the defect emissions with microstructural disorder. These advanced characterisation techniques provide powerful ways to detect defects in photovoltaic devices and guide strategies to mitigate their adverse effects and increase device efficiency.
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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.