Jk. Arch et al., CONTRIBUTION OF SILICON SUBSTRATES TO THE EFFICIENCIES OF SILICON THIN-LAYER SOLAR-CELLS, Solar energy materials and solar cells, 45(4), 1997, pp. 309-322
Although silicon solar cells based on layers less than 50 mu m thick h
ave become very popular, little attention has been paid to the role of
the underlying silicon substrate. This treatment uses the device simu
lation program PC-1D and the ray tracing program SUNRAYS to examine th
e role of the substrate in contributing to the current and efficiency
of textured and non-textured thin layer solar cells. For the case of a
heavily doped silicon substrate, substrate contributions can be signi
ficant for cells with sufficiently thin base layers. For example, for
the case of a silicon thin layer cell with a base layer thickness of 2
0 mu m and a substrate doping of 6 X 10(18) cm(-3), the substrate cont
ributes no more than 4% of the total short-circuit current. However, d
ecreasing the base width to 5 mu m results in an increase in this subs
trate contribution to 20%. Light trapping tends to alleviate the subst
rate contribution by increasing the effective path length in the base.
Examination of the current components under forward bias reveals that
for a thin layer cell with a high quality base and good front surface
passivation, back diffusion of electrons into the substrate limits ce
ll performance.