Longi has released a heterojunction back contact (BC) solar cell made using a laser-enhanced contact optimisation process. It requires about one-third of the total effective processing time of mainstream technologies such as PERC and TOPCon. The cell is based on dense passivating contacts that contain less hydrogen than the common contacts used in BC cells. It can be used in all silicon-based PV application scenarios, and helps reduce parasitic light absorption while improving passivation.
The device comprises a 243.0 cm2 cell with an M6 phosphorus-doped n-type Czochralski monocrystalline silicon wafer. It deposits the dense passivating contacts via plasma-enhanced chemical vapour deposition at 240 °C. A pulsed green picosecond laser with a spot of 250 μm is used to ablate the films. The champion cell has achieved a power conversion efficiency of 27.3 per cent. It has also reportedly demonstrated 26.2 per cent efficiency for HBC solar cells metallised by screen-printed low-temperature copper paste.
