Here　we　report　a　certified　efficiency　of　up　to　25.11%　for　silicon　heterojunction　(SHJ)　solar　cells　on　a　full　size　n-type　M2　monocrystalline-silicon　(c-Si)　wafer　(total　area,　244.5　cm(2)).　An　ultra-thin　intrinsic　a-Si:H　buffer　layer　was　introduced　on　the　c-Si　wafer　surface　using　a　13.56　MHz　home-made　RF-PECVD　with　low　deposition　rate　showing　superior　surface　passivation.　The　ultra-thin　i-a-Si:H　film　with　both　higher　microstructure　factor　(R*)　and　H　content　evidently　increases　the　SHJ　solar　cell　open-circuit　voltage　(V-OC)　by　2　mV,　and　moreover,　short-circuit　current　(I-SC)　and　fill　factor　(FF)　are　also　notably　improved,　resulting　in　a　0.52%　absolute　cell　efficiency　enhancement,　in　which　FF　is　the　main　cause.　In　order　to　explore　high　conversion　efficiency　SHJ　solar　cells,　both　home-made　RF-PECVD　and　commercial　VHF-PECVD　(40.68　MHz)　are　employed　for　deposition　of　the　i-a-Si:H　passivation　layer.　As　a　result,　the　efficiency　of　RF-PECVD-prepared　SHJ　cell　is　0.21%　higher　than　that　of　VHF-PECVD-prepared,　mainly　driven　by　V-OC　and　I-SC　boost.　This　work　offers　a　useful　tool　for　fabrication　of　high　performance　SHJ　solar　cells　which　could　be　employed　in　mass　production.