Efficient interdigitated back‐contacted silicon heterojunction solar cells

We present back‐contacted amorphous/crystalline silicon heterojunction solar cells (IBC‐SHJ) on n‐type substrates with fill factors exceeding 78% and high current densities, the latter enabled by a SiN x /SiO 2 passivated phosphorus‐diffused front surface field. V oc calculations based on carrier lifetime data of reference samples indicate that for the IBC architecture and the given amorphous silicon layer qualities an emitter buffer layer is crucial to reach a high V oc , as known for both‐side contacted silicon heterojunction solar cells. A back surface field buffer layer has a minor influence. We observe a boost in solar cell V oc of 40 mV and a simultaneous fill factor reduction introducing the buffer layer. The aperture‐area efficiency increases from 19.8 ± 0.4% to 20.2 ± 0.4%. Both, efficiencies and fill factors constitute a significant improvement over previously reported values. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)