Recombination at Metal-Emitter Interfaces of Front Contact Technologies for Highly Efficient Silicon Solar Cells

We present an experimental approach to extract the dark saturation current density j(0e-met) at the emitter-metal interface of the front contact. For this purpose, 2x2 cm(2) sized silicon solar cells have been realized featuring different metallization fractions F-M. By simply applying the one-diode-model, the dark current density j(01) is determined from the open circuit voltage V-oc. From the slope of the j(01) over F-M plot, j(0e-met) is extracted. However, this is only valid if the dominant recombination mechanism at V-oc features a diode character that is close to unity. Hence, the local ideality factor m is determined from the suns-V-oc-curve indicating the required value close to one. Three main effects are observed. First, the metallization methods which are compared show different influences on j(0e-met) on the same emitter configuration. Second, an emitter drive-in due to an additional short thermal oxidation lowers j(0e-met). Also, the field-effect passivation of the highly n-doped selective emitter decreases j(0e-met) effectively. By combining the field effect passivation with a short drive-in step the very low value of j(0e-met) = 549 fA/cm(2) is reported. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of SiliconPV 2011.