There seems to be a lot of confusion about efficiency. For a single junction solar cell (like the type of solar cell talked about in the article) the theoretic

There seems to be a lot of confusion about efficiency. For a single junction solar cell (like the type of solar cell talked about in the article) the theoretical efficiency is 34% (under 1 sun illumination). The best a silicon device can do is ~29% because silicon has a slightly lower than ideal bandgap. Single junction solar cells made out of GaAs have gotten to ~31% efficiency because GaAs has an ideal bandgap. However, GaAs is super expensive. Achieving 26% efficiency when the theoretical efficiency for silicon is 29% is super impressive. Engineers have basically squeezed every ounce of potential real world performance out of single junction silicon solar cells.