Hybrid solar cells based on blends of poly(N-vinylcarbazole) (PVK) and silicon nanowires (SiNWs) as electron donor and electron acceptor have been fabricated. The effects of thermal annealing on the photoluminescence and device performances of hybrid photovoltaic cells have been investigated. The influence of the annealing temperature and time on the charge transfer process between PVK and SiNWs has been investigated by the quenching of the PVK photoluminescence in correlation with the morphology changes of the hybrid layer which has been characterized by scanning electron microscopy. The photovoltaic parameters have been significantly improved by heat treatment. The device performance enhancement obtained under optimized annealing temperature and time is mainly due to improved donor/acceptor morphology in the active layer strongly affecting the transport pathways for free charges and contact to the electron-collecting electrode.