UNDERSTANDING AND QUANTIFYING THE IMPACT OF AL PASTES ON AL BACK SURFACE FIELD SCREEN-PRINTED SILICON SOLAR CELL

摘要

Uniform and thick back surface field (BSF) introduced by Al paste are the key features of a high efficiencyconventional Al-BSF silicon solar cell. The Al particle morphology and printed thickness as well as the peak firingtemperature can influence the BSF thickness. Several commercial Al pastes exhibit different BSF thicknesses because ofthe varying printed thickness and hence the variation in open circuit voltage (V_(oc)). To quantify the variation in BSFthickness and Voc, large area (239 cm~2) p-type CZ 2.6 ohm·cm solar cells were fabricated on commercial 65 ohm/□ emitterusing Al paste from three different manufacturers A, B and C. The best cells obtained with Al pastes A, B and C showedsimilar V_(OC) and J_(SC). The 2 mV ΔV_(OC) observed is consistent with the variation in BSF thickness which could arise fromdifference in printed Al, BSF uniformity and BSRV. The result was confirmed by SEM and IQE analyses and the ELmeasurements confirmed the series resistance difference was due to the front Ag contacts. PC2D simulation was alsoemployed to investigate the effect from variation of Al pastes by matching the experimental EQE curves.