  In the last years, liquid-scintillator detectors have opened a new window for
the observation of low-energetic astrophysical neutrino sources. In 2007, the
solar neutrino experiment Borexino began its data-taking in the Gran Sasso
underground laboratory. High energy resolution and excellent radioactive
background conditions in the detector allow the first-time spectroscopic
measurement of solar neutrinos in the sub-MeV energy regime. The experimental
results of the Beryllium-7 neutrino flux measurements as well as the prospects
for the detection of solar Boron-8, pep and CNO neutrinos are presented in the
context of the currently discussed ambiguities in solar metallicity. In
addition, the potential of the future SNO+ and LENA experiments for
high-precision solar neutrino spectroscopy will be outlined.
