NOVELTY - Photovoltaic cell (10) material system comprises an absorbing structure (12) with two sides (121, 122). A first layer (14) is attached to the first side. It receives light beams from exterior with a third side and reflecting light beams from the absorbing structure with a fourth side. A second layer (16) is attached to the second side and reflects light beams from the absorbing structure. Photo resonance is implemented within the absorbing structure by the first layer associated with the second layer.    USE - The material system is used for photovoltaic cell, e.g. solar cell.    ADVANTAGE - Material system traps most of the incident light beams within an absorbing structure with two high-reflection layers toward the absorbing structure, to efficiently utilize incident light beams. It enhances the photovoltaic efficiency. It reflects most of light beams back to an absorbing structure. Photos will be absorbed efficiently within the resonance cavity and converted into electrons. The association of the two layers traps the light beams into the absorbing structure and cause micro-resonance cavity in the absorbing structure. Photo resonance is formed within the absorbing structure to enhance photovoltaic efficiency.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a photovoltaic cell with resonance cavity comprising a first structure of reflection attached to one side of a resonance cavity and for reflecting light beams from the resonance cavity. A second structure of reflection is attached to other side of the resonance cavity and reflects light beams from exterior and the resonance cavity. The absorber layer is made of semiconductor compound. The front and back conductors are made of semiconductor materials doped differently each other. The first layer comprises an anti-reflection coating at the third side. It comprises a high-reflection coating (HR coating) at the fourth side, and the high-reflection coating has a reflectivity substantial in excess of 99.8%. The second layer is made of dielectric material of Distributed Bragg Reflector (DBR). The second layer and the second structure of reflection are made of dielectric material, insulating material, and/or semiconductor material.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional diagram illustrating the structure of material system for a photovoltaic cell.    Photovoltaic cell (10)    Absorbing structure (12)    First layer (14)    Second layer (16)    Sides (121,122)