  We show that liquid organic scintillator detectors (e.g., KamLAND and
Borexino) can measure the 8B solar neutrino flux by means of the nu_e charged
current interaction with the 13C nuclei naturally contained in the
scintillators. The neutrino events can be identified by exploiting the time and
space coincidence with the subsequent decay of the produced 13N nuclei. We
perform a detailed analysis of the background in KamLAND, Borexino and in a
possible liquid scintillator detector at SNOLab, showing that the 8B solar
neutrino signal can be extracted with a reasonable uncertainty in a few years
of data taking. KamLAND should be able to extract about 18 solar neutrino
events from the already collected data. Prospects for gigantic scintillator
detectors (such as LENA) are also studied.
