Impact of the contacting scheme on I-V measurements of metallization-free silicon heterojunction solar cells
Institute for Solar Energy Research Hamelin, Am Ohrberg 1, 31860 Emmerthal, Germany
2 Leibniz University of Hanover, Am Welfengarten 1, 30167 Hannover, Germany
3 Institute of Energy and Climate Research 5–Photovoltaic, Research Center Juelich, 52425 Juelich, Germany
4 Meyer Burger GmbH, An der Baumschule 6-8, 09337 Hohenstein-Ernstthal, Germany
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Received in final form: 17 December 2022
Accepted: 10 March 2023
Published online: 26 April 2023
I‑V measurements are sensitive to the number and positioning of current and voltage sensing contacts. For busbarless solar cells, measurement setups have been developed using current collection wires and separate voltage sense contacts. Placing the latter at a defined position enables a grid resistance neglecting measurement and thus I‑V characteristics independent from the contacting system. This technique has been developed for solar cells having a finger grid and good conductivity in the direction of the fingers. The optimal position of the sense contact in case of finger-free silicon heterojunction solar cells has not yet been studied. Here, the lateral charge carrier transport occurs in a transparent conductive oxide layer resulting in a higher lateral resistance. We perform finite difference method simulations of HJT solar cells without front metallization to investigate the impact of high lateral resistances on the I-V measurement of solar cells. We show the high sensitivity on the number of used wires for contacting as well as the position of the sense contact for the voltage measurement. Using the simulations, we are able to explain the high difference of up to 7.5% in fill factor measurements of metal free solar cells with varying TCO sheet resistances between two measurement systems using different contacting setups. We propose a method to compensate for the contacting system to achieve a grid-resistance neglecting measurement with both systems allowing a reduction of the FF difference to below 1.5%.
Key words: Heterojunction solar cell / I‑V measurement / contacting / fill factor / metal-grid free / module integration
© M. Brinkmann et al., Published by EDP Sciences, 2023
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.