NOVELTY - A spectrally adaptive photovoltaic device (100) comprises photovoltaic modules, substrate, insulating layer, and junction(s) (111-113). The photovoltaic modules are disposed one on top of another. Each module includes two conductive layers and at least two semiconductor layers disposed between the conductive layers. The two semiconductor layers define a junction at an interface between them. The two semiconductor layers of each module are non-single crystalline thin film layers. The photovoltaic modules are staked on the substrate.    USE - A photovoltaic device for converting optical energy to electrical energy in spectral adaptive manner (claimed).    ADVANTAGE - The device has conversion efficiency that is less dependent on spectral content of the optical energy than corresponding device where current matching is applicable. The device also improves optical spectral responsivity.    DETAILED DESCRIPTION - A spectrally adaptive photovoltaic device comprises photovoltaic modules, substrate, insulating layer, and junction(s). The photovoltaic modules are disposed one on top of another. Each module includes two conductive layers and at least two semiconductor layers disposed between the conductive layers. The two semiconductor layers define a junction at an interface between them. The two semiconductor layers of each module are non-single crystalline thin film layers. The photovoltaic modules are staked on the substrate. The insulating layer is between adjacent photovoltaic modules. The junction converts a first spectral portion of optical energy into an electrical voltage and transmits a second spectral portion of optical energy to another of the junctions that is configured to convert the second spectral portion of optical energy in electrical voltage. The modules include at least three modules. The junctions collectively have solar energy conversion efficiency of greater than 20%. At least two of the junctions have semiconductor bandgaps that are different from each other. The semiconductor layer comprises copper indium gallium selenide (CIGS)- or cadmium-based semiconductor materials, semiconducting polymers, and organic composite materials. The two conductive layers comprise transparent conducting layers. The insulating layer comprises transparent insulating layer. The device includes reflecting coating, and textured surface for scattering unabsorbed part of optical energy. An INDEPENDENT CLAIM is included for converting optical energy to electrical energy in spectral adaptive manner.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of thin film multi-junction photovoltaic device with spectral adaptive capabilities.    Spectrally adaptive photovoltaic device (100)    Light (101)    Bandgap (102, 103)    Junctions (111-113)    Electrical contacts (140)