A new range of optically clear encapsulants are available from this company. RTV27844 is a crystal clear, low viscosity, two-part silicone that cures at room temperature to a high strength rubber with a thermal conductivity of 0.45 W/mK. It can be used in potting solar cells and assemblies where component identification is desirable.
PU22985 is a two-part water clear potting polyurethane which cures to form a 85 Shore A material with good abrasion and hydrolysis resistance and thermal conductivity of 0.3 W/mK. It was reportedly developed for the potting of luminaires, LEDs and doming applications.