Bandgap Boosts Solar Cell Efficiency with Nanowires

The average efficiency of standard commercial solar cells has been increased by 0.4 percent, just by replacing the standard surface texture with nanowire technology, Bandgap Engineering Inc. announced this week.

The nanowire-enhanced cells, produced on the same line as the standard cells, showed an average efficiency boost from 17.2 to 17.6 percent, Bandgap said.

To demonstrate the boost, Bandgap asked a cell manufacturer to run 84 multicrystalline wafers through its standard industrial cell process, including a standard emitter, standard silicon-nitride and standard screen printing with full back-side aluminum metal, on standard full-area 156 × 156-mm wafers. The only difference was that half the wafers in the batch featured Bandgap’s patented nanotexture, while the other half had standard acidic texture.

The single-sided nanotexture, a drop-in upgrade for crystalline silicon manufacturers, enables processes that require planar back surfaces for improved reflection or passivation. The texturing process also consumes less than 1 µm of silicon, which is ideal for thin silicon technologies, the company said. The silicon nanowires can also be patterned to enable plated front metal contacts without laser patterning or lithography.
“The best nanowire solar cell had 17.76 percent efficiency, compared to 17.32 percent for the best standard solar cell. Since the cell process was optimized for the standard cells, and not for nanowire cells, and since we have a clear path to further improve our technology, I expect further efficiency improvements with a fairly straightforward optimization,” said Dr. Jeff Miller, Bandgap’s senior device scientist.

Bandgap had previously demonstrated even larger efficiency improvements, but that was by optimizing the full cell process for nanowire cells, the company said.

Separately, the company also announced a new efficiency record of 19 percent for a monocrystalline nanowire solar cell made in collaboration with the Georgia Institute of Technology. Importantly, all the cells, including the record-setting cell, were full-area, 156 × 156-mm cells produced with a standard emitter, silicon-nitride, full-back-side aluminum metal and screen-printed metallization, Bandgap said.

For more information, visit: www.bandgap.com