NOVELTY - A photovoltaic module comprises a transparent electrode, two tuned and transparent photovoltaic layers (B, C) of doped silicon, a second transparent electrode, a non-conductive transparent separation layer (E), a third transparent electrode, two tuned photovoltaic layers (G, H) of doped silicon tuned to complement the transparent photovoltaic layers, and a fourth transparent electrode. All module components are sandwiched between window glasses. The innermost glass may be insulated single or double glass pane. The windowpanes and module components are mounted in a two-part frame.    USE - Photovoltaic module for installation into a prebuilt and prewired receptor window opening, and for use as skylights in a structure. (All claimed)    ADVANTAGE - The photovoltaic module generates usable electric current through its photovoltaic function, completes light filtering task by blocking/capturing solar energy such as infrared or UV, and can replace windows. By using photovoltaic module to replace conventional window, there is an immediate cost benefit or cost offset. If transparent alumina is utilized during module fabrication, occupant security is increased because transparent alumina is stronger than steel of the same thickness. The transparent alumina increases the strength of panel, provides the building more resistance to bullets, and provides higher level of blast protection than glass alone. This is beneficial for high profile buildings, structures, or occupants at increased risk to sustain violence; and provides a higher level of protection from certain types of extreme weather damage.    DETAILED DESCRIPTION - A photovoltaic module comprises a transparent electrode; two tuned and transparent photovoltaic layers of doped silicon including P-type layer and N-type layer; a second transparent electrode; a non-conductive transparent separation layer of glass or optically transparent alumina; a third transparent electrode; two tuned photovoltaic layers of doped silicon including P-type layer and N-type layer and tuned to complement the transparent photovoltaic layers; and a fourth transparent electrode. The four layers of doped silicon are identically patterned with voids of greater than or equal to 1.5 mm. All module components are sandwiched between window glasses. The innermost glass may be insulated single or double glass pane formed from optically transparent alumina. The windowpanes and module components are mounted in a two-part frame. Mylar(RTM: thin polyester film) is attached to the interior window frame. All the components are framed in an aluminum structure.    DESCRIPTION OF DRAWING(S) - The drawing is a layered view of a photovoltaic module and its frame.    Conductive transparent contact grids (A, D, F, I)    Tuned and transparent photovoltaic layers of doped silicon (B, C)    Non-conductive transparent separation layer (E)    Tuned photovoltaic layers of doped silicon (G, H)