silicon surfaces and compared the total and quantum efficiency
with solar cells made with other texturing techniques that were
discussed in the previous section. The silicon nanowire (Si nw)
technique has also been included, which is similar to the porous
silicon surface. The height of nanowires here are about 3–4 mm
compared to the 300 nm tall nanowires for the porous silicon
case. The photovoltaic device parameters for the four different
types of solar cells are summarized in Table 2. All the devices in
Table 2 have similar emitter doping concentrations, surface
passivation layers and alloyed aluminum back surface field to
ensure a fair comparison.
The device with a chemically textured surface and SiNx as the
ARC is used to benchmark solar cells with other surface texturing
schemes. It is evident from Table 1 that the ultrafast laser
texturing scheme results in the highest short-circuit current
density of 39.2 mA/cm2 and is a clear indication of superior light
trapping. However, the device displays a conversion efficiency of
over 14% due to a lower open-circuit voltage. We believe that
proper optimization of surface dopant concentration, removal of
laser-induced defects and a better surface passivation layer will
improve the Voc. The silicon nanowire scheme also shows a very
promising current density value with a conversion efficiency of
13.7%. The porous silicon solar cell reported by NREL shows the
best conversion efficiency of around 16.8% and a short-circuit
current density of 34.1 mA/cm2. The question now arises as to
why there is a significant variation in the short-circuit current
density among the different surface texturing schemes even
though all of them have reflection losses below 5–6%. Hence, in
order to gain a further insight on the impact of surface texturing