This
work illustrates a technology for advanced light management
by introducing a nonconventional back reflector layer (BRL) in amorphous
silicon (a-Si:H) solar cells. To meet this, silver sulfide (Ag2S) nanoparticles with ∼50 nm diameter have been chosen
as the nanomirror owing to its low parasitic absorption loss over
a broad wavelength (300 to 1100 nm) region. The Ag2S NPs
were sandwiched between two indium tin oxide (ITO) layers and placed
as the back reflector layer of an a-Si:H solar cell to achieve better
light trapping within the active layers. The embedded structure exhibited
high reflectance (up to 93%) in the red and near-infrared region,
the main working zone of a-Si:H cells. With the incorporation of such
a state-of-the-art back reflector structure in a-Si:H solar cells,
a photoconversion efficiency of 10.58% has been achieved, which is
one of the best in this class.
The advantages of the amorphous silicon (a-Si)/crystalline silicon (c-Si) hetero junction technology are low temperature (<200 °C) processing and fewer process steps to fabricate the device. In this work, we used indium tin oxide (ITO) nanoparticles embedded in amorphous silicon material at the rear side of the crystalline wafer. The nanoparticles were embedded in silicon to have higher scattering efficiency, as has been established by simulation studies. It has been shown that significant photocurrent enhancements (32.8 mA cm−2 to 35.1 mA cm−2) are achieved because of high scattering and coupling efficiency of the embedded nanoparticles into the silicon device, leading to an increase in efficiency from 13.74% to 15.22%. In addition, we have observed a small increase in open circuit voltage. This may be due to the surface passivation during the ITO nanoparticle formation with hydrogen plasma treatment. We also support our experimental results by simulation, with the help of a commercial finite-difference time-domain (FDTD) software solution.
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