As mentioned in Section 3.1, the p-type and n-type doped
poly-SiOx CSPCs with 2-step annealing technique are used
as the hole and electron contacts in DST solar cells, respectively. The
change in passivation after different fabrication steps for the DST
solar cell precursor is shown in Figure 5(b). The increase in
passivation after hydrogenation and its decrease after ITO deposition
are as expected. However, unlike the SST case, the loss in passivation
after TCO deposition is not fully recovered after hydrogen annealing at
400 °C for 1 hour. This is because the DST solar cell precursor has
p-type doped CSPC applied to the textured side, which is the limiting
factor in terms of passivation and does not recover its passivation even
after such a hydrogen annealing. The best DST solar cell gave a
certified designated area PCE of 19.44% (Voc = 655 mV,
Jsc = 37.85 mA/cm2, FF = 78.42%,
metallization faction ~3%, designated area = 3.903
cm2, see Figure 5(d)). Compared to the SST solar cell,
despite suffering from poorer surface passivation as witnessed by the
lower Voc and FF, the DST cell exhibits higher
Jsc. This gain can be ascribed to the textured rear side
of the DST solar cell which promotes a more efficient light scattering
at the rear side and thus higher absorption in the c-Si bulk. Figure
6(a) shows the EQE of the SST and DST devices. As expected, the EQE of
the DST cell outperforms that of the SST cell at wavelengths above 800
nm.