Presentation Details
| Capacitance-Based Metastability in Samples Extracted from UV-Stressed Silicon TOPCon Photovoltaic Modules Steve Johnston, Dana B.Kern, Rebecca B.Wai, Kent Terwilliger. National Laboratory of the Rockies, Golden, CO, USA |
Abstract
A commercially available TOPCon module is stressed with UV light at ~60°C and a dose of 67.5 kWh/m2. The power degradation, which is mostly voltage loss, is 3.5% after dark storage and 2.3% after light recovery. Some cells within the module show more metastability, and cell fragments are extracted from cells showing relatively high and low metastability. Capacitance on each sample is measured over a frequency range of 100 Hz to 1 MHz. Applied forward bias of 0.5 V, temperatures above ~280 K, and frequencies below 10 kHz combine to give a larger capacitance value. The depletion width is collapsed toward the front junction, and higher temperatures and longer times allow more charges to overcome potential barriers and emit from trap states to contribute to the capacitance. Using these parameters, capacitance is measured over 4 to 5 weeks from the light recovered state to the dark storage state. Throughout this transition, capacitance increases ~1 and 2% for relatively low- and high-metastability samples, respectively.
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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.