In this work, n-type silicon based solar cells with WO3/Ag/WO3 multilayer films\nas emitter (WAW/n-Si solar cells) were presented via simple physical vapor deposition\n(PVD). Microstructure and composition of WAW/n-Si solar cells were studied\nby TEM and XPS, respectively. Furthermore, the dependence of the solar cells\nperformances on each WO3 layer thickness was investigated. The results indicated\nthat the bottom WO3 layer mainly induced band bending and facilitated\ncharge-carriers separation, while the top WO3 layer degraded open-circuit voltage\nbut actually improved optical absorption of the solar cells. The WAW/n-Si solar\ncells, with optimized bottom and top WO3 layer thicknesses, exhibited 5.21%\nefficiency on polished wafer with area of 4 cm2 under AM 1.5 condition (25 ââ??¦C\nand 100 mW/cm2). Compared with WO3 single-layer film, WAW multilayer films\ndemonstrated better surface passivation quality but more optical loss, while the\noptical loss could be effectively reduced by implementing light-trapping structures.\nThese results pave a new way for dopant-free solar cells in terms of low-cost\nand facile process flow.
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