The single digit efficiency metric is probably overall conversion efficiency of sunlight. The two efficiencies are probably quantum yield, or the efficiency at

The single digit efficiency metric is probably overall conversion efficiency of sunlight. The two efficiencies are probably quantum yield, or the efficiency at converting one wavelength of light. We have two because the molecule's tristable. Converting from state 0 to 1 has one efficiency while converting from state 1 to 2 has another. State 0 and 1 also absorb different wavelengths of light. Because sunlight's a mix of different wavelengths not just the two our molecule's active at, the efficiency at sunlight conversion will be different than the quantum efficiency.