NOVELTY - The solar cell (100) has pn junctions (102,104) having n-type regions, p-type regions and a first and a second band-gap energy. A transparent electrically insulating layer (106) is provided between the pn junctions that are connected in parallel to form a two-terminal photonic device. The pn junction comprise layers of copper indium gallium selenide (sulfide) (CIGS), copper zinc tin sulfide (CZTS), a-Si, polycrystalline Si, microcrystalline Si, cadmium telluride (CdTe) alloyed with Zn, Se or S. A bottom pn junction is provided with Ge or GaAs region.    USE - Tandem voltage-matched monolithic thin film multi-junction solar cell.    ADVANTAGE - The material removal from the top pn junction is eliminated to access the underlying pn junction layer for processing. The light absorption in the Si active layers can be improved and implementation of interdigitated back contact (IBC) can be carried out at low cost. The dependence on crystalline growth template can be mitigated, thus the need for thick CGTB layers is obviated and the growth complexity and material usage in the device are reduced. The absorption of long wavelength light through light-trapping effects can be improved. The need for crystalline growth template for the polycrystalline or amorphous thin film layers is eliminated. The use of inexpensive, non-crystalline substrates, such as glass, and light trapping can be achieved that incorporate crystalline Si pn junction. The need for heavily doped tunnel junctions is eliminated. The overall performance of the sub-cells is enhanced.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a method for fabricating tandem voltage-matched solar cell; and    (2) a method for fabricating voltage-matched thin film multi-junction solar cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the tandem voltage-matched solar cell.    Voltage-matched solar cell (100)    Pn junctions (102,104)    Transparent electrically insulating layer (106)    Sub cell strings (108,110)