Mass production of industrial tunnel oxide passivated contacts (i-TOPCon) silicon solar cells with average efficiency over 23% and modules over 345 W

摘要

We present an industrial tunnel oxide passivated contacts (i-TOPCon) bifacial crystalline silicon (c-Si) solar cell based on large-area n-type substrate. The interfacial thin SiO2 is thermally growth and in situ capped by an intrinsic poly-Si layer deposited by low-pressure chemical vapor deposition (LPCVD). The intrinsic poly-Si layer is doped in an industrial POCl3 diffusion furnace to form the n(+) poly-Si at the rear, which shows an excellent surface passivation characteristics with J(0) = 2.6 fA/cm(2) when passivated by a SiNx:H layer deposited by plasma-enhanced chemical vapor deposition (PECVD). With an industrial fabrication process, the cells are manufactured with screen-printed front and rear metallization, using large-area 6-in. n-type Czochralski (Cz) Si wafers. We demonstrate an average front-side efficiency greater than 23% and an open-circuit voltage V-oc greater than 700 mV. These results are based on more than 20 000 pieces of cells from mass production on a single day, in an old conventional multicrystalline silicon (mc-Si) Al-back surface field (BSF) cell workshop, which has been upgraded to i-TOPCon process. The best cell efficiency reaches 23.57%, as independently confirmed by Fraunhofer CalLab. A median module power greater than 345 W and a best module power greater than 355 W are demonstrated with double-glass bifacial i-TOPCon modules consisting of 120 pieces of half-cut 161.7 mm pseudosquare i-TOPCon cells with nine busbars.