Note that converting sunlight to electricity (what the 30% figure is about) is also quite different from using sunlight to convert CO2 to glucose (what the 6% figure is about).

Apparently the first stage of photosynthesis effectively does convert sunlight to electricity and does that with 90% efficiency, which is far beyond what our technology can achieve.

Source: https://www.economist.com/the-economist-explains/2014/12/03/...