Silicon　heterojunction　solar　cells　have　shown　great　advantage　due　to　their　large　open-circuit　voltage　which　induces　a　high　energy　conversion　efficiency.　However,　the　short-circuit　current　density　is　limited　by　the　high　light　absorption　of　an　n-type　amorphous　silicon　window　layer　in　the　short-wavelength　range.　Here　an　amorphous　silicon　oxide　film　was　introduced　to　replace　the　window　layer.　The　increasing　oxygen　content　in　amorphous　silicon　oxide　layers　leads　to　the　enlarged　optical　band　gap　and　the　enhanced　short-wavelength　transmittance.　As　a　result,　the　short-circuit　current　density　increases　obviously　which　comes　from　the　high　transmittance　of　amorphous　silicon　oxide　films　due　to　the　wider　band　gap.　Furthermore,　the　highly　phosphorous-doped　amorphous　silicon　layer　was　introduced　to　improve　the　contact　between　transparent　conductive　oxide　layer　and　n-type　amorphous　silicon　oxide　layer.　The　carrier　transport　property　is　enhanced　and　thus　the　fill　factor　increases　significantly.　Finally,　a　silicon　heterojunction　solar　cell　with　an　area　of　238.95　cm(2)　was　prepared,　yielding　a　total-area　efficiency　up　to　21.1%.　Overall,　the　results　indicate　that　amorphous　silicon　oxide　films　can　be　applied　to　silicon　heterojunction　solar　cells　as　a　window　layer,　which　provides　a　new　route　to　obtain　higher　energy　conversion　efficiency.