Abstract Experiments P-type multicrystalline silicon wafer with a


Abstract

In this paper, we proved that the combination
of Aluminum/Porous silicon treatment give an excellent passivation of multicrystalline
silicon surface. Photoconduction system (WCT-120) and Infra-Red absorption techniques were used
to quantified the surface passivation level. Consequently of this treatment,
the effective lifetime (?eff) raises from 1.9 ?s to 100 ?s. In additional we demonstrate that this process
not only grant a high passivation of multicrystalline silicon substrate but also
decreases the surface reflectivity in the wavelength range 1100-350 nm, starting
of 30% for untreated sample to ?2% for Aluminum/Porous silicon treated ones. In addition, this
amelioration is characterized by a significant reduction in effective surface
recombination Seff (i.e. 1.5 cm s?1), which resulted
a high efficiency mc-Si solar cell.

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Keywords:
mc-Si nanostructure; surface treatment; porous silicon;FTIR; liftime ;
silicon solar cell.

1.      Introduction

Multicrystalline silicon surface passivation is ever
more important in PV. For high-efficiency multicrystalline silicon solar cells,
an admirable level of surface passivation is a requisite. Multicrystalline
Silicon wafers habitually contain a large amount of impurities and defects that
badly affect the effective lifetime and thus cell efficiency. To conquer this
problem, new process is needed to accomplish both surface and bulk passivation
such as, using coating based on silicon nitride (SiNx), silicon
oxide (SiO2) 2,3, indium tin oxide (ITO) 4,5,6,  ultrathin gold (Au) 7–9, silver (Ag)
10–12 and copper (Cu) 13.We investigate in this work, the antireflection and
passivation attain by Aluminum/Porous silicon treatment on
multicrystalline silicon surface. The effect of combined treatments based
aluminum /PS on the optoelectronic properties of multicrystalline silicon were
discussed.

 

 

 

2.
Experiments

P-type multicrystalline silicon wafer with a thickness of 280 µm and a resistivity of 0.5?2 W cm were used in this
experiment.   Chemical surface treatment
with (1:3:5;HF/HNO3 /H2SO4)
solution after screen printing an aluminum (Al) layer Annealed at 5000C
was performed to eliminate the portion of the solid layer of Al. The p + doped
silicon surface is treated with HF/HNO3 /H2O2
solutionsto obtain the porous silicon (PS) nanostructures. The
chemical etching (CE) processes were applied to mc-Si wafers with a surface area of 4 cm2using
optimal immersion time in a 1:2:4 HF (48 wt %) /HNO3
(65 wt %) /H2O2 solutions to form PS on the surface of p + doped mc-Si.
To prevent the PS film from deteriorating, immediately following PS construction,
the multicrystalline silicon samples were cleaned and dried with DI water and
N2 flux, respectively. The multicrystalline
silicon surface
morphology before and after stain etching treatment was investigated by AFM and
scanning electron microscope
(SEM). The total reflectivity of multicrystalline silicon surface was measured using a UV-Vis-NIR
spectrophotometer with an integrating sphere. Finally, the effective lifetime
was calculated in a photoconduction (WCT-120 system).

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