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 SiNx/SiO2 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.