HJT: Advantages

Advantage 1: Short process flow. The HJT battery process mainly includes four steps: velvet making, amorphous silicon deposition, TCO deposition, and screen printing; Far fewer than PERC (10) and TOPCON (12-13). Among them, amorphous silicon deposition mainly uses PECVD method. There are currently two methods for TCO film deposition: reactive plasma deposition (RPD) and physical chemical vapor deposition (PVD). Sumitomo Heavy Industries holds a patent for RPD, while PVD technology has matured and there are many manufacturers providing equipment.

Advantage 2: High conversion efficiency. Mainly due to the dual passivation effect of N-type silicon substrate and amorphous silicon on surface defects of the substrate. At present, the mass production efficiency is generally above 24%; More than 25% of the technical route is already very clear, which is to use doped nanocrystalline silicon, doped microcrystalline silicon, doped microcrystalline silicon oxide, and doped microcrystalline silicon carbide on the front and rear surfaces instead of existing doping; HJT's future stacking of IBC and perovskite conversion efficiency may be improved to over 30%.

Advantage 3: No LID and PID, low attenuation. Due to the fact that the substrate of HJT cells is usually N-type single crystal silicon, which is phosphorus doped and does not contain boron oxygen or boron iron complexes in P-type silicon, HJT cells are immune to the LID effect. The surface of HJT battery is deposited with TCO film without insulation layer, so there is no chance of surface layer charging, which avoids PID occurrence structurally. HJT cells experience a 1-2% decline in the first year and an annual decline of 0.25% thereafter, which is much lower than the decline of gallium doped PERC cells (2% decline in the first year and 0.45% decline annually thereafter). Therefore, the power generation per W of the entire lifecycle of HJT cells is about 1.9% -2.9% higher than that of double-sided PERC cells.

Advantage 4: Low temperature coefficient and high power generation. The power temperature coefficient of HJT cells is usually -0.25 to 0.2%/℃, which is lower than the -0.45%/° C to -0.35%/° C of conventional and PERC cells. The low temperature coefficient of HJT means that in high-temperature operating environments of components, HJT batteries have relatively high power generation performance, thereby achieving power generation gain and reducing the system's electricity cost per kilowatt hour. If considering that the operating temperature of the battery exceeds the ambient temperature by 10-40 ℃, and the annual average ambient temperature is 5-10 ℃ lower than the laboratory standard operating conditions, the HJT battery generates about 0.6% -3.9% more electricity per W than the double-sided PERC battery.

Advantage 5: High double-sided rate. The front and back structures of HJT are symmetrical, and the TCO film is transparent, making it a natural double-sided battery. The double-sided rate of HJT can reach over 90% (up to 98%); The double-sided rate of double-sided PERC is only 75%+. According to SolarZoom's calculations, considering 10% -20% backside irradiation and the difference in double-sided rate of solar cells, HJT cells generate approximately 2% -4% more electricity per watt than double-sided PERC cells.

Advantage 6: Weak light effect. HIT cells use N-type monocrystalline silicon wafers, while PERC cells use P-type monocrystalline silicon wafers. Under irradiation intensities below 600W/m, the power generation performance of N-type cells is about 1% -2% higher than that of P-type cells; HJT cells generate approximately 0.5-1.0% more electricity per watt than double-sided PERC cells due to weak light effects.

Overall, the power generation per watt of double-sided HJT cells throughout their entire lifecycle is significantly higher than that of double-sided PERC cells, with a relative advantage of around 7%.

HJT: Industrialization Progress - Economic Efficiency

The current high cost is an important factor limiting the large-scale industrialization of HJT technology.

1. The HJT and PERC process routes are completely different and cannot be extended. Only new production lines can be established, and HJT is not compatible with mainstream PERC production equipment. Therefore, the investment in PECVD and other film making and vacuum equipment will bring high conversion costs to enterprises.

2. HJT battery cost structure: silicon wafer cost, non silicon materials (silver paste, target materials, gases, chemicals, etc.), equipment depreciation, other manufacturing expenses (including labor and power costs), etc.