25.11% efficiency silicon heterojunction solar cell with low deposition rate intrinsic amorphous silicon buffer layers

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 cm2). 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 (VOC) by 2 mV, and moreover, short-circuit current (ISC) 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 VOC and ISC boost. This work offers a useful tool for fabrication of high performance SHJ solar cells which could be employed in mass production.