The PI (photosynthesis-irradiance) curve is a graphical representation of the empirical relationship between solar irradiance and photosynthesis. A derivation of the Michaelis–Menten curve, it shows the generally positive correlation between light intensity and photosynthetic rate. Plotted along the x-axis is the independent variable, light intensity (irradiance), while the y-axis is reserved for the dependent variable, photosynthetic rate.

Source for above quote and pictures below: https://www.wikiwand.com/en/PI_curve

Above about 10,000 lux or ~100 watts/square meter the rate no longer increases. Thus, most plants can only utilize ~10% of full mid-day sunlight intensity.[6]

Source: https://www.wikiwand.com/en/Photosynthetic_efficiency

An irradiance between 400 and 800 µE m^-2 s^-1 seems to be the best option since 1000 µE.. would reqiure far more energy.

I should probably build two different modules. One 400 µE... and one 800 µE... .