Partners Reach Efficiency Milestone With n-PERT Solar Cells
Electronics Weekly, April 14, 2016. Image credit: juliacasado1
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.