abstract
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 ofthe sense contact incase offinger-free siliconheterojunctionsolar cells hasnot yet beenstudied.Here, the lateralchargecarrier transport occurs inatransparentconductiveoxidelayer resultinginahigherlateral resistance. We perform finite difference method simulations of HJT solar cells without front metallization to investigate the impact ofhigh lateral resistances on the I-Vmeasurement ofsolar cells.We showthe high sensitivity on thenumber of used wires for contacting as well as the position of the sense contact for the voltage measurement. Using the simulations,weareable toexplainthehighdifferenceofupto7.5%infill factormeasurementsofmetal freesolarcells 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%.Beteiligte Forschungsgruppen
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