deposit an i a-Si layer on the silicon surface, which is referred from
the passivation technology in solar cells [24–27]. Comparisons have
been carried out for the passivation effects between the samples
passivated by these two methods and the ones without passivation
(H-terminated). For the samples passivated by these two methods,
a silica or i a-Si insert layer was introduced between the silicon and
the PEDOT:PSS, respectively. This intercalation acts as a barrier, so
its thickness has great influence on the internal electric field thus
exerting influence on carrier separation according to the quantum
tunneling theory. Therefore, it is of great necessity to control the
thickness of the silica or i a-Si intercalation. After a great deal of
tests (given in the supporting information), we find that the optimal
process for the native oxidation method is to treat the silicon
wafer for 12 hat roomtemperature inair condition; andthe optimal
process for the i a-Si passivation method is to deposit the intrinsic
amorphous silicon at 250 ◦C for 20 s. What’s shown in Fig. 2 are the
TEM images of the silicon surface passivated by an i a-si layer and
silica layer, corresponding to the optimized process. It can be found
that the passivation layers had apparent boundaries with the c-Si
substrate. The thickness of the optimal i a-si layer is about 2 nm,
while that of the silica layer is about 1.5 nm.
To characterize the passivation effects, we measured the minority
carrier lifetimes of the silicon wafers treated by above two
technologies, as shown in Fig. 3. From which we can see that the
i a-Si passivation is the best method. The minority carrier lifetime
of the silicon wafer passivated by an i a-Si, about 41.35 s,