24.47%, comparable to p-type HJT of n-type

CEA INES, a French research institute, has developed p-type wafers for the production of heterojunction cells and introduced gallium doping into the production of p-type cells, resulting in heterojunction cells with performance comparable to n-type, with an optimum conversion efficiency of 24.47%, Global PV has learned.

HJT PV cells can be made from either n-type or p-type silicon wafers. For large scale expansion of HJT, cheaper p-type wafers may be preferred, however p-type cells are less efficient than n-type and exhibit instability in specific cases of boron doping. work by CEA INES has shown that the production process for high performance post-junction bifacial n-type cells can be applied to front-junction p-type cells without changing the process, with efficiency losses as low as 0.3%.

Photovoltaic manufacturers are starting to replace boron doping with gallium around 2019 as a solution for photo-induced degradation caused by the reaction between boron and oxygen. in August 2022, research at Fraunhofer ISE in Germany showed that with gallium doping, p-type wafers can achieve similar or even higher cell efficiencies than n-type wafers.

Fraunhofer ISE has produced a silicon ingot with a higher resistivity due to gallium doping

"For this reason, we propose to use the p-type HJT cells with gallium doping that we obtained on a semi-industrial test line, which are essentially stable under mild light and have an efficiency close to that of the n-type." CEA INES said.

In September this year, Longi achieved a conversion efficiency of 26.12 percent for silicon heterojunction cells on a gallium-doped p-type full-size (M6, 274.3 cm2) monocrystalline silicon wafer, which is the highest efficiency record for p-type silicon cells to date, and Jagatron's existing HJT equipment can also be used for silicon heterojunction cell (p-HJT) technology made from gallium-doped p-type silicon wafers.