Analysis of Series Resistance Losses in a-Si:H/c-Si Heterojunction Solar Cells

We present an experimental method to quantify the series resistance R
_a-Si/ITO
through the a-Si:H layers and the a-Si:H/ITO interface on test structures. In order to optimize R
_a-Si/ITO
, we apply different a-Si:H and ITO deposition parameters. We find the best value for R
_(p)-a-Si/ITO
of 0.42 Ω·cm
²
for an ITO double layer with a 10-nm-thin starting layer that provides good contact resistance and an additional 90-nm top layer that provides good conductivity. For R
_(n)-a-Si/ITO
, we reach values below 0.1 Ω·cm
²
. We present an analysis of the series resistance and shading losses of our 100-cm
²
bifacial screen-printed a-Si:H/cSi heterojunction solar cells, which show an open-circuit voltage of V
_oc
= 733 mV, demonstrating the excellent level of interface passivation. The efficiency of 20.2% is limited by a low short-circuit current density of 37.1 mA/cm
²
and fill factor of 76%.