Figure 9 TTe in the wavelength range of 400-2300 nm for IHfO:H films
annealed at different temperatures.
As the annealing temperature increases, both the transmission and
reflection spectra change significantly due to the change in refractive
index caused by the rise in crystallinity (Figure
S3).37 In order to eliminate the effect of reflection
on transmission, the effective total transmittance (TTe) spectra are
used instead of the transmission spectra to evaluate the optical
properties of the IHfO:H films annealed at different
temperatures,38 as shown in Figure 9. TTe is defined
as \(\text{TTe}=\frac{T}{(1-R)}\), where T is the transmittance and
R is the reflectance. When the annealing temperature is below or equal
to 150 °C, the TTe of the IHfO:H films remains almost unchanged in the
visible region while slightly increases in the NIR region. After the
annealing temperature increases to 200 °C, the average TTe of the IHfO:H
films increases from 88.54 % to 91.16 % in the visible region which
can be related to better crystallization with less
defects.39 Meanwhile, the average TTe significantly
increased from 77.14 % to 95.61 % in the NIR region. According to the
Drude model, FCA is proportional to carrier
concentration.34 Thereby, the IHfO:H films annealed at
temperature above 200 °C behave higher transmittance as they have lower
carrier concentration as shown in Figure 7.
Overall, the post-annealing treatment shows a significant impact on the
crystallinity, the electrical properties, and the optical transmission
of the IHfO:H films. Considering the above opto-electronic
characteristics comprehensively, the appropriate annealing temperature
is about 200 °C which is within the temperature tolerance range of the
SHJ solar cells.
3.3 Application of the IHfO:H films on SHJ solar cells