HJT cells, also known as HIT cells or heterojunction cells, are crystalline silicon heterojunction solar cells. They are silicon solar cells that utilize a HIT structure, a technology that involves depositing amorphous silicon thin films onto crystalline silicon. Combining the core advantages of crystalline silicon cells and thin-film cells, they improve photoelectric conversion efficiency and are a popular trend in high-efficiency silicon-based solar cells.
I. Advantages of Heterojunction (HIT) Batteries
1. Wide range of applications: HIT batteries play an indispensable role in various economic fields such as solar panels, urban public transportation, communication equipment, power installation projects, national defense technology, ocean voyages, and domestic aviation.
2. High potential for efficiency improvement: The N-type silicon wafers used in HIT cells have a higher minority carrier lifetime, and the corresponding structure with amorphous silicon passivation treatment can also achieve a lower surface recombination rate. As a result, the open-circuit voltage of silicon heterojunction solar cells is much higher than that of traditional monocrystalline silicon solar cells, and its efficiency potential is up to 2% greater than that of current PERC cells using P-type silicon wafers.
3. Low cost and simple production process: HIT batteries combine the advantages of ultra-low temperature manufacturing of thin-film solar cells, avoiding the traditional high-temperature processes. The HIT process is relatively simple, requiring only four steps to complete the entire production process.
4. High stability and high efficiency: HIT batteries have good light stability. No Staebler-Wronski effect was found in the amorphous silicon thin film in the heterojunction, which means that the battery conversion efficiency will not show any signs of degradation due to light exposure.
5. Double-sided battery: HIT battery is an excellent double-sided battery with virtually no color difference between the front and back sides. Moreover, the bifaciality (the ratio of the efficiency of the back side to the efficiency of the front side) can reach over 90%, and can even reach 98% in some cases. The core competitive advantage of generating electricity from the back side is obvious.
II. Disadvantages of Heterojunction HIT Batteries
1. High equipment investment: Due to the use of thin film deposition technology, high-performance vacuum equipment is required.
2. The process requires strict control to obtain a low-interface-state amorphous silicon/crystalline silicon interface, which also places high demands on the process environment and operation.
3. Transparent conductive films are generally made of indium oxide-doped metal oxides, which have a high cost. The high resistivity of low-temperature silver paste leads to high silver paste consumption per unit.
4. Low-temperature module packaging technology is required. Due to the low-temperature process characteristics of HJT cells, the high-temperature packaging technology of traditional crystalline silicon cells cannot be used. It is necessary to develop a suitable low-temperature packaging technology.
