Production process for mono cast solar cell surpassing 23% effectiveness

• Trina Solar has actually made a PV cell by directly applying the unmodified i-TOPCon process, initially created for Cz mono wafers, to cast n-type quasi-mono silicon wafers. It claims the typical effectiveness, examined in-house with an adjusted recommendation cell, is 22.98%.

Researchers from China's State Key Lab of Photovoltaic Science as well as Technology, Trina Solar, as well as Australia-based Amrock Group have actually released a clinical paper that supplies understanding into how the panel maker was able to attain a 23.22% conversion effectiveness and also an open circuit voltage (Voc) of 711.9 mV for a bifacial polycrystalline solar cell established with mono cast innovation.

Trina announced the outcomes, separately validated by ISFH CalTeC in Germany, in November 2019. The three celebrations explained their searchings for in "Industrial TOPCon solar cells on n-type quasi-mono Si wafers with efficiencies over 23%," recently published in Solar Energy Materials and also Solar Cells. They applied a TOPCon layout (industrial tunnel-oxide passivated call) to a 2 x 2 square-centimeter area of an 157.4 mm x 157.4 mm quasi-mono n-type wafer with 180 μm thickness. They used an alkaline cleaning as well as structure procedure to the wafer.

The wafer was passivated with a piled dielectric film complied with by a thermal therapy in a firing heater to turn on the passivation, after saw damages was removed. The reliable life time of the wafer is stated to be near to the bulk life time, due to the surface passivation; the researchers explained this as "superb.".

" The i-TOPCon process originally established for Czochralski (Cz) mono wafers could be directly applied without adjustment to the actors quasi-mono wafers and also supply exceptional passivation on the front and also back side," the scientists claimed.

They evaluated the process difference in between Cz monocrystalline product as well as cast mono material by preparing in parallel cells made by Cz as well as quasi-mono wafers. "By comparison, in the quasi-mono cells, the bulk recombination is dominating the power loss, while the losses at the front side are minimized as well as are proportionally much less damaging," they discussed.

They declared that the typical efficiency of the cell, tested internal with a calibrated reference cell, is 22.98%. "The power loss analysis provided by Sinton FCT-450 validated that the mass recombination of quasi-mono plays a dominating role, unlike in Cz mono cells, where the recombination in the emitter is mainly limiting the performance," the scientists claimed, keeping in mind that the Sinton FCT-450 is a flash tester made use of for in-house IV measurements of solar cells.

The researchers stated they might even more maximize the cell efficiency in the future when the top quality of bulk products boosts. "Further examination reveals that a reduced opposite saturation present density (J0) of front and also rear might achieve a Voc over 710 mV despite having the reasonably reduced mass lifetime," they stated.

Mono cast solar cells are generated with seeded cast silicon, which is also known as cast-mono or quasi-mono crystalline silicon. The cast mono process allows the manufacturing of 'mono like' wafer product using a modified multicrystalline heating system and also prevents expensive investment in ingot pulling equipment. Cast-mono wafers are much less prone to recombination triggered by boron-oxygen issues and have the advantage of reduced light-induced degradation.

Cast mono producing emerged at the beginning of the decade, yet its significance has actually faded due to an absence of assembly line capability. Nevertheless, with extra efficient monocrystalline panels going beyond multi as the market criterion, multicrystalline producers have gone back to cast mono technology to stay clear of the expenditure of retooling their manufacturing capacities.

Canadian Solar said last year that it had attained 22.8% efficiency for its p-type multicrystalline P5 solar cell, based upon mono cast innovation. Just a few months earlier, rival GCL Systems Integration had introduced cast mono technology modules with 18.9% effectiveness.