In certain laminators for poly (ethylene-co-vinyl acetate) (EVA) encapsulation process of photovoltaic modules, cooling press (CP) is applied to the module after encapsulation. Here, the effect of CP on the optical transmission through common PV encapsulants is studied. Interestingly, CP is shown to reduce drastically the scattering of the light between 400 and 700nm traveling through the thermoplastic polyolefin (TPO)-based encapsulant. Post-annealing tests prove this effect to be stable at the temperature up to 85 degrees C. This work has discovered a simple solution to mitigate the milky appearance of the TPO encapsulant and hence greatly enhanced its competitiveness against EVA.