1. What is HJT?

HJT solar cells: that is, amorphous silicon thin film heterojunction solar cells. It is a heterojunction composed of two different semiconductor materials. Crystalline silicon heterojunction solar cell (HJT) is a thin film of amorphous silicon deposited on crystalline silicon. It combines the advantages of crystalline silicon solar cells and thin film solar cells, with high conversion efficiency, low process temperature, high stability and attenuation. With the advantages of low power rate and double-sided power generation, the technology is subversive.

2. Why are you optimistic about HJT Photovoltaic? 

The essence of solar cell panel technology iteration is that cost reduction and efficiency improvement, high efficiency and low cost are the direction of development.

HJT is the development direction of a new generation of solar cell technology because of its high photoelectric conversion efficiency, high bifacial ratio, simplified equipment process, low product light attenuation, strong stability, large space for cost reduction and efficiency enhancement, and broad prospects.

Comparison of several solar cells: 

1) PERC: The process flow of PERC solar cells is relatively simple and the equipment is mature. In the past two years, some efficiency improvement processes have been standard, such as laser SE, alkali polishing, optical injection/electric injection, etc. The PERC technology is mainly based on the deposition of the passivation layer on the backside and laser grooving. On this basis, the front-side SE laser and optical injection/electrical injection annealing and other processes are added when the process is improved and optimized.

  2) TOPCon: First, a 1-2nm tunnel oxide layer is prepared on the back of the solar cell, and then a layer of doped polysilicon is deposited. The two together form a passivation contact structure, providing good interface passivation for the back of the silicon wafer. .

  3) HJT: N-type single crystal silicon (C-Si) is used as the substrate light absorption area, and after texturing and cleaning, an intrinsic amorphous silicon film (i-a-Si: H ) and doped P-type amorphous silicon (P-a-Si:H), and the silicon substrate forms a p-n heterojunction. The backside of the silicon wafer is formed by depositing i-a-Si:H and doped N-type amorphous silicon (n-a-Si:H) with a thickness of 5-10nm to form a back surface field. ), and finally formed metal-based electrodes on the top layers of both sides by screen printing, which is a typical structure of heterojunction solar cells.

  4) IBC: A solar cell in which both the p+ doped region and the n+ doped region are placed on the back of the solar cell (non-light-receiving surface). The light-receiving surface of the IBC solar cell is not blocked by any metal electrodes, thereby effectively increasing the short-circuit current of the solar cell. , so that the energy conversion efficiency of solar cells is improved.

Comparison of the highest laboratory efficiency of photoelectric conversion: PERC is 24%; TOPCon is 26%, which is a small area laboratory record of 4 cm in Germany, and the highest commercialization efficiency of Jinko is 25.4% in a large area; HJT is LONGi M6 laboratory The latest data reaches 26.5%, while the theoretical efficiency of HJT+perovskite tandem solar cells can reach 43%.

At present, the average efficiency of mass-produced microcrystalline HJT is 24.95%, and the yield rate is 96.4%, which has obvious advantages in efficiency improvement compared with other solar cells.

UNITED ENERGY is also closely following the industry trend. It has started to deploy the HJT production line since the end of 2022, and it is expected to be officially put into production by the end of 2023!