ITO-Free Silicon Heterojunction Solar Cells With ZnO:Al/SiO2 Front Electrodes Reaching a Conversion Efficiency of 23%

Silicon heterojunction (SHJ) solar cells have been increasingly attracting attention to the photovoltaic community in the last years due to their high efficiency potential and the lean production process. We report on the development of a stable baseline process for SHJ cells with focus on the optical improvement of the solar cells' front side. An amorphous silicon oxide layer (a-SiO2) was used as an antireflective coating (AR) on the front side the finished SHJ devices. Both optical simulations and experimental results demonstrate a short-circuit current density (J(sc)) improvement of 0.4 mA/cm(2) when applying the a-SiO2 AR, yielding maximum conversion efficiencies of 23.0%. Full-size cells with 244 cm(2) total area have been produced using three front contact stacks: indium tin oxide (ITO) as reference, ZnO:Al, and ZnO:Al/SiO2 showing the J(sc) improvement with the double AR configuration. Damp-heat tests on those samples demonstrate an enhanced stability of cells with ZnO:Al front TCO when capped with SiO2.