TiO_2/porous silicon nanocomposite passivation coating for mc-Si wafers

摘要

This work reports on passivation effect of solar-grade multicrystalline Si (mc-Si) using a TiO_2/porous silicon double coating. For this purpose, TiO_2 nanoparticles were deposited onto porous silicon (PS)/mc-Si using pulsed laser ablation of titanium target. The structural and optoelectronic properties of the TiO_2/PS treated mc-Si substrates were investigated by X-ray diffraction, Raman spectroscopy, optical spectrometry, photo-conductance and photoluminescence (PL). It was found that the minority carrier lifetime (τ_(eff)) of the mc-Si wafer could enhance at a nominal thickness of the TiO_2 film (nanoparticle sizes). This was attributed to a surface passivation of the mc-Si wafer via TiO_2-passivation of the PS film, whose PL intensity improves consequently. An optimal TiO_2 thickness of 80 nm was found to give the highest PL intensity and an enhancement of the minority carrier lifetime from 5 us for untreated mc-Si wafer to about 391 us for a TiO_2/ PS treated wafers.