The interrelation of photoluminescence (PL) properties and open circuit voltage (V-oc) of thin film p-i-n microcrystalline silicon (muc-Si:H) solar cells with efficiencies above 9% was studied. Hot wire chemical vapour deposition (HW-CVD) technique was used for the preparation of intrinsic layer at various silane concentrations (SC). The effect of the tail states on the splitting of the quasi-Fermi energies and carrier distributions was studied by monitoring V-oc and PL energy as a function of temperature and optical generation rate (g(o)). An increase of the PL energy and V-oc is observed for (i) increasing SC, (ii) increasing g(o) and (iii) decreasing temperature. It is also found that (i) V-oc and PL energy are limited by the band tail states and (ii) short circuit current density drops at low temperatures. The latter effect is attributed to a reduced carrier extraction due to trapping of the carriers in band tail states and subsequent recombination. It is proposed that increasing SC leads to a reduction of the density of band tail states due to structural relaxation of the muc-Si:H network by the presence of hydrogen or hydrogenated amorphous silicon. (C) 2003 Elsevier B.V. All rights reserved.