High efficiency solar cells on electromagnetic cold crucible cast multicrystalline silicon

Electromagnetically cold crucible casted multicrystalline silicon (EMC) has been recently introduced as a potentially cheap, and clean material for solar cells. Improving the bulk quality of EMC material by hydrogen plasma passivation is investigated here. In this work it is suggested and confirmed that, due to the small grain size and to the low oxygen content in EMC silicon, hydrogen passivation would be very effective. Solar cells are fabricated following a high efficiency process and the effect of the hydrogen plasma treatment on the cell performance is studied by means of efficiency and spectral response measurements. A very significant increase in the short circuit current and in the open circuit voltage is obtained due to the back side hydrogen plasma passivation resulting in an efficiency of 14.2% on 10×10 cm² and a maximum efficiency of 15.7% on 2×2 cm² cells. This 15.7% efficiency is the highest ever reported on EMC multicrystalline silicon. The comparison between the spectral responses of hydrogenated and of nonhydrogenated cells confirms the role of the plasma hydrogen passivation in substantially improving the diffusion length of the EMC material