Belgium-based nanoelectronics research center imec and Crystal Solar, a California-based company focused on direct wafer-growing technologies, say they have achieved a 22.5% cell efficiency with n-type PERT (passivated emitter, rear totally diffused) silicon solar cells manufactured on six-inch mono-crystalline epitaxially grown kerfless wafers.
According to the companies, Crystal Solar’s manufacturing technology called Direct Gas to Wafer enables direct conversion of feedstock gas to mono-crystalline silicon wafers by high throughput epitaxial growth. By skipping the polysilicon, ingoting and the wire-sawing steps altogether, this approach cuts costs and reduces the capital required to set up a manufacturing plant, they continue.
Imec has adapted its n-PERT Si solar cell process to align with the properties of Crystal Solar’s kerfless wafers. The 156 mm2 x 156 mm2 cells were fabricated on 160 um to 180 um thick grown n-type wafers with built-in rear p+ emitter. Imec’s n-PERT process included a selective front surface field realized by laser doping, advanced emitter surface passivation by Al2O3 and Ni/Cu plated contacts. The companies claim the process resulted in record efficiencies for homojunction large-area solar cells of 22.5% and a record open circuit voltage of 700 mV.
“We are extremely happy to have achieved such high conversion efficiencies on n-PERT solar cells processed from kerfless wafers using imec’s pre-pilot industrial silicon PV manufacturing line,” says Jozef Szlufcik, PV department director at imec. “The combination of our advanced cell process and the innovative wafer manufacturing technique of Crystal Solar is paving the way for manufacturing of highly efficient solar cells at substantially lower cost and will be disruptive for the complete solar manufacturing value chain.”
T.S. Ravi, CEO of Crystal Solar, says the company expects to achieve >23% efficiencies with imec’s PERT technology “in the very near future.”