Scientist Make Instance for Gallium-doped p-type Heterojunction Solar Cells

• Australian-Russian Research team has actually created Gallium-doped p-type SHJ solar cell wafers.
• They are 22.6% efficient with better stability and also cheaper costs.

Scientists of an Australian-Russian research team have come out with a technique to make Silicon Heterojunction Solar Cells based on P-type wafers much more efficient and stable with Gallium-doping.

These p-type, Gallium-doped wafers have proved to be 22.6% effective, a lot more steady, and less costly than the normal n-type Phosphorus-doped Czochralski-- grown up silicon (Cz-- Si) wafers.

The scientists of the research team from the University of New South Wales (UNSW) in Australia and Russian heterojunction solar module producer Hevel Solar think that these wafers may emerge as a main remedy for the SHJ section in the coming years.

According to the researchers, the existing n-type phosphorus-doped Czochralski-- grown silicon (Cz-- Si) wafers ensure no sensitivity to the boron-oxygen light-induced degradation (B-O LID) that is normal for p-type boron-doped wafers and also drastically influences the performance of SHJ cells in time.

Although n-type wafers make sure even more stability generally, they are presently much more pricey to create than p-type wafers, which are the mainstream option for the manufacturing of PERC (passivated emitter and rear call) cells. So, using p-type wafers may potentially minimize the prices for the heterojunction technology, since wafer costs still stand for 40% of a cell's overall cost.

How Was the New technology Developed?

The expiration of Shin Etsu's gallium doping patent (US6815605B1) has actually urged the solar market to adopt p-type gallium-doped Cz-Si wafers, according to the research group.

Researchers created two solar cells with a brand-new advanced hydrogenation process (AHP) at an existing SHJ line run by Hevel making use of 156.75 × 156.75 mm p-type wafers doped with boron (B) and also gallium (Ga), respectively. The very first products were provided by Chinese maker Longi as well as the 2nd by Taiwanese wafer manufacturer Sino-American Silicon (SAS). For recommendation, researchers also created the typical n-type SHJ tool.

All the wafers initially treated with a potassium hydroxide (KOH) saw-damage etch as well as KOH anisotropic texturing. B-doped hydrogenated amorphous silicon (a-Si: H) layers were transferred in the rear side of the wafers as well as inherent and also P-doped (a-Si: H) layers were after that deposited in the front of the wafers making use of a plasma-enhanced chemical vapor deposition (PECVD). In the final action, indium-tin tin-oxide (ITO) transparent conductive oxide (TCO) layers were transferred on both sides via physical vapor deposition.

According to the researchers, the cell built with B-doped wafers exhibited an effectiveness of 20.5% as well as an open-circuit voltage of 719.6 mV, while the Ga-doped tool was found to have a performance of 22.6%, a fill aspect of 78.2%, an open-circuit voltage of 730 mV and no degradation throughout light-soaking.

The research group indicated that the conversion effectiveness of the gallium-doped SHJ solar cells is still lower than the n-type reference cells, which was high due to a decreased fill variable (FF). More job is required to overcome this FF constraint to promote high-efficiency gallium-doped SHJ solar cells.

The next steps would call for understanding the specific needs for different SHJ solar cell manufacturers with different toolsets as well as processing problems. The expenses would certainly coincide as for methods addressing LID/LeTID in p-type PERC cells and when advanced hydrogenation devices are implemented for commercial n-type SHJ solar cells as well as TOPCon solar cells, the UNSW scientist informed.

So, the researcher group assumes p-type wafers have the potential to handle the n-type SHJ solar cell wafers. The research team published the total procedure of solar cells advancement and solar cell as well as the relevant hydrogenation procedure in a paper qualified, "Stability Study of Silicon Heterojunction Solar cells made with Gallium- and also Boron-doped Silicon Wafers", published in RRL Solar.