HJT Solar cell technology in 2020
HJT ( Heterojunction) solar cell are N-type.
HJT ( Heterojunction) cells which are solar cells made of crystalline silicon (c-Si) and amorphous silicon (α-Si) films. Al-BSF and PERC are made of P-type silicon. Photo-induced attenuation (LID) refers to the percentage of power loss after a component is first exposed to light. Second, due to the higher doping levels commonly used in PERC cells, the negative effects of LID will increase after PERC technology is used. There is no LID phenomenon in N-type solar cell. Under the same doping condition, the photoelectric conversion efficiency of N-type solar cell is higher than that of P-type solar cell. With the market's increasing emphasis on photoelectric conversion efficiency, N-type solar cell are expected to become a future trend. Therefore, HJT is expected to become the mainstream of the next generation of N-type solar cell.
HJT solar cell technology is simpler than PERC and PERT. The main processes include texturing and cleaning, growing amorphous silicon film, double-sided TCO (transparent conductive film) plating, screen printing, and sintering.
HJT solar cell technology advantages:
1) Higher photoelectric conversion efficiency. PERC solar cell conversion efficiency is 22% -23%, HJT solar cell mass production efficiency has reached 23% -24%, and the theoretical efficiency is as high as 27%.
2) The process flow is short. Compared with the 7-step core process of PERC solar cell, the core process of HJT solar cell has only 4 steps: velvet cleaning, amorphous silicon coating, TCO coating and screen printing.
3) Low attenuation. First of all, HJT uses N-type solar cell, there is no LID phenomenon; secondly, TCO film is deposited on the surface of HJT solar cell, there is no insulation layer, so there is no surface with motor, so there is no PID (potential induced attenuation) effect.
4) The double-sided rate is higher. HJT solar cell double-sided rate can reach more than 90%, PERC is generally 75%. The 60 version solar cell pack has 10W more effective power than PERC.
Disadvantages of HJT solar cell: HJT solar cell production equipment is expensive and investment costs are high. At present, the cost of HJT solar cell equipment for 1GW is 8 billion to 1 billion yuan, and 1GW for PERC solar cell is about 300 million yuan.
HJT solar cell have four core processes and rely on four main types of equipment:
There is a slight difference between velvet cleaning equipment and PERC solar cell equipment. HJT cleaning equipment is compatible with hydrogen peroxide and ozone.
The amorphous silicon coating process can use two types of equipment: Cat-CVD and PECVD.
TCO coating process can choose two types of equipment: PVD and RPD.
HJT solar cell screen printing process is slightly different from PERC solar cell. The printing process is similar, and the subsequent drying and sintering processes are different. Mainly because PERC solar cell use high temperature silver paste, while HJT solar cell use low temperature silver paste.
Before 2015, aluminum back-field solar cell were the most mainstream solar cell; from 2015 to 2019, PERC solar cell rose rapidly. The 2017-2019 global PERC new capacity will be 20GW, 40GW, and 59GW, and it is expected that there will be 40GW expansion in 2020. HJT solar cell (heterojunction solar cell) have higher conversion efficiency, lower attenuation, and shorter process flow. HJT solar cell are expected to accelerate into the introduction period in 2020.