NOVELTY - An optically transparent element comprises an optically transparent substrate (2); and an anti-reflective coating (1) disposed on at least one surface of the optically transparent substrate, where the anti-reflective coating comprises a polymer, the polymer comprises at least one first tetraalkoxy silane residue; and at least one second alkoxy silane residue selected from trialkoxy silanes, dialkoxy silanes and/or monoalkoxy silanes, where the polymer comprises at least 50 mole% of the tetraalkoxy silane residue based on the total moles of polymer.    USE - As optically transparent element (claimed) such as photovoltaic (PV) modules e.g. solar cell; in anti-reflective coatings used in glass covers.    ADVANTAGE - The optically transparent element has improved hardness, adhesion, shelf-life and/or processing efficiency. The coating solutions remain stable for at least 24 hours to about 4 weeks. The coating solutions can be stored in a -20 to -40 degrees C freezer for up to at least six months without materially impacting the optical or mechanical properties desired for glass coatings. The ability to preserve anti-reflective coatings for an extended period of time may provide a significant manufacturing advantage, particularly if the coating solution is transported to an off-site location and/or stored for a period of time prior to use. The optically transparent element has improved light transmittance characteristics e.g. the anti-reflective coating has a refractive index of 1.3 or less and a pencil hardness of at least 2H. The anti-reflective coating reduces reflections of the incident light and permits more light to reach the thin film semiconductor film of the photovoltaic module thus permitting the device to act more efficiently.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of photovoltaic cell including an anti-reflective coating.    Anti-reflective coating (1)    Transparent substrate (2)    Transparent electrode (3)    Semiconductor film (4)    Reflector (6)