N-type c-Si cell has high minority carrier lifetime, no light-induced attenuation (LID), good low-light effect, low temperature coefficient, is expecting towards the theoretical highest efficiency of c-Si solar cells. ITRPV 2018 forecasts N-type silicon wafer market share will continue to increase, with nearly 10% in 2020, and 28% in 2028. N-type c-Si solar cells mainly include N-PERT/N-PERL cell, interdigitated back contact (IBC) cell and heterojunction (HJT) cell. In Aug. 2017, Kaneka’s HBC (HJT+IBC) cell efficiency has achieved a record of 26.63%.
N-PERT and N-PERL cells have simple structure, large potential to enhance efficiency, and can achieve bifacial power generation. Jolywood, YingLi and Linyang have been achieved mass production of high efficiency N-type mono-Si bifacial cell. Passivated contact technology is an important development direction of N-type cell, can greatly improve the conversion efficiency. Passivated contact is realized by the tunneling oxide layer and the doped polysilicon layer on the rear side of cell, to achieve passivation on the rear side without opening, avoiding silicon material damage and high recombination velocity at the opening. In May 2018, Jolywood signed a contract with SPIC Huanghe Hydropower, and will deliver 5GW N-type bifacial TOPCon (Tunnel Oxide Passivated Contact) cells in 2019-2021.
HJT has advantages of high conversion efficiency, simple low-temperature manufacturing process, thin wafer applications, low temperature coefficient and CTM, bifacial power generation. The key to achieving low-cost mass production of HJT cells is the localization of equipment, improved yield and productivity, and reducing costs for wafers, low-temperature silver paste, TCO targets, cleaning and texturing chemicals. Gold Stone, Jinneng and CIE Power have achieved mass production of HJT cells. In 2018, Tongwei, Akcome, Caihong, etc. begin the construction of HJT cell capacities.
IBC cell’s P-N junction and electrodes are all on the back, completely eliminating the gate line shading of front surface, the average mass production efficiency is up to 23%. But IBC cell requires high quality wafer, and production processes are complicated, so the cost is high. Using industrial technologies in the production line, such as screen printing, tube diffusion or ion implantation, is the key to achieving low cost IBC cell. And the use of passivated contact technology can improve the efficiency of IBC cells. At the beginning of 2018, Trina Solar's 6-inch IBC cell achieved a full-area efficiency of 25.04%. In Aug. 2018, Huanghe Hydropower officially started construction of 200MW IBC cell and module project.
3rd N Type c-Si Cell and Passivated Contact Forum 2018will be held on 6-7 December in Changzhou, Jiangsu, China. The upcoming conference will discuss PV industrial outlook & N-type solar cell & bifacial module market, N-type silicon wafer quality improvement, thinning & cost reduction prospect, N-PERT/N-PERL, HJT & IBC cells key equipment and process optimization for mass production, passivated contact technology in N-type cell application and efficiency improvement prospect, N-type solar cell and passivated contact metallization & advanced pastes, N Type bifacial、MBB and shingled module real power generation benefits, etc.
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