INFLUENCE OF THE BOTTOM WO_3 LAYER ON THE SERIES RESISTANCE IN SILICON BASED SOLAR CELLS WITH WO_3/AG/WO_3 EMITTER

摘要

The silicon based solar cells was fabricated on n-type CZ silicon wafer, employing triple-layer WO_3/Ag/WO_3 films as emitter, cesium carbonate (Cs_2CO_3) as back surface field (BSF), referred to as WAW/n-Si solar cells. All of those films were deposited by physical vapor deposition (PVD) at room temperature. In this work, series resistance (R_s) in WAW/n-Si solar cells, mainly comprising all the film's series and contact resistances, were quantitatively analyzed and discussed. The results indicated that contact resistivity (ρ_c) for n-Si/WO_3 contact is strongly dependent on bottom WO_3 layer thickness. 10～20 nm-thick bottom WO_3 layer is needed for WAW/n-Si solar cells with favorable R_s. When optical performance was taken into consideration, WAW/n-Si solar cells of 9.47% best efficiency was achieved on polished silicon substrate under STC (AM 1.5 global spectrum, 25 °C and 1000 W/cm~2). In absence of the effect of R_s, efficiency of 11.52% can be reached.