Analytical and numerical solutions were developed to assess the effects of introducing a nanofluid for optical filtration (OF) above the PV module and a layer of a nano-enhanced phase change material (nanoPCM) below the PV panel, on the overall performance of a photovoltaic-thermal solar collector. The analytical study employed six models (M1-M6) with different arrangements of the cooling channel, optical filtration channel, nanoPCM and the number of optical filtration passes. The optical fluid demonstrated an enhancement in the performance by cooling the PV module by convection beside the optical filtration effect. A numerical study was undertaken to distinguish the effects of the optical fluid in enhancing the performance of the photovoltaic thermal system. The numerical study employed three extra models (N1-N3), which use cooling and optical filtration only. The optical filtration fluid channel and the PV module are separated by an airgap in N-1, while in N-2 the optical filtration channel is directly above the PV module. Optical filtration is not used in N-3. The effect of the channel height, nanoparticle concentration, and mass flow rate on the performance was evaluated. The analytical results show that the use only of a nanoPCM decreases the overall efficiency (thermal + electrical) by about 6.7% (neglecting the storage effects of the nanoPCM). However, the introduction of optical filtration makes the decrease in efficiency very small ( < 1%). Moreover, using the optical filtration alone improves the overall efficiency by 6-12%. The thermal performance can be improved if the optical fluid channel and the PV panel are separated by an airgap. However, this may reduce the electrical efficiency.