Presentation Details
| The Ambiguity of Capacitance Derived Carrier Density and a Theoretical Revision of the Depletion Approximation Mayank Mate, Amit Munshi. Colorado State University, Fort Collins, CO, USA |
Abstract
Capacitance-Voltage (C-V) measurements have proven useful to extract carrier densities in polycrystalline CdTe photovoltaics (PV). However, these PV devices have defect states within the bandgap. Further, modern CdTe absorbers are graded with Se, making it difficult to pinpoint the formation of the space charge region. The defects and band grading due to Se alloying result in fluctuations in the capacitance, as measured by C-V and can lead to systematically distorted or non-physical carrier density extraction. In this work, we investigate the phase angle and capacitance changes during the C-V measurement and narrow down the bias and depletion width regime to provide clarity about carrier densities. We also demonstrate the indeterminate nature of calculating dopant activation from C-V and Secondary Ion Mass Spectroscopy (SIMS) analysis of incorporated dopant species. Finally, we propose a phenomenological extension to the depletion approximation that captures the experimentally observed evolution of depletion width in compensated, graded CdTe junctions.
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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.
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