Sara Olibet

Stretched-exponential a-Si:H/c-Si interface recombination decay

The electronic properties of hydrogenated amorphous silicon (a-Si:H) relax following stretched exponentials. This phenomenon was explained in the past by dispersive hydrogen diffusion, or by retrapping included hydrogen motion. In this letter, the authors report that the electronic passivation properties of intrinsic a-Si:H/crystalline silicon (c-Si) interfaces relax following a similar law. Carrier injection dependent a-Si:H∕c-Si interface recombination calculations suggest this originates from amphoteric interface state (or Si dangling bond) reduction, rather than from a field effect. These findings underline the similarity between a-Si:H∕c-Si interface recombination and the electronic properties of a-Si:H bulk material.

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700 mV

Crystalline silicon wafer (c-Si) can be extremely well passivated by plasma enhanced chemical vapor deposited (PECVD) amorphous silicon (a-Si:H) films. As a result, on flat substrates, solar cells with very high open circuit voltage are readily obtained. On textured substrates however the passivation is more cumbersome, likely due to the presence of localized recombinative paths situated at the pyramid valleys. Here, we show that this issue may be resolved by selecting a silicon substrate morphology featuring large pyramids. Chemical post-texturization treatments can further reduce the surface recombination velocity. This sequence has allowed us to fabricate solar cells with open circuit voltage over 700 mV, demonstrating also on device level the effect of pyramid density and surface micro-roughness on the surface passivation quality.