Extra terrestrial solar irradiance

Hai marpet,
I was trying to get Es at 1nm interval from sentinel-2.
Es is the equivalent extra-terrestrial solar spectrum and depends on the spectral response of the SENTINEL-2 bands.I found F0 in terms of 13 bands . can you tell me the relation between Es and spectral response function and How can I get Es at 1nm interval .Is there any reference or guides which I can follow.