NOVELTY - The cell (100) has a p-n junction including a p-type layer and an n-type layer, where each of the p-type and n-type layers of material includes an intermediate band (IBand) and the material includes dilute III-V nitride material and gallium arsenide with nitrogen concentration ranging from 0.5-5 percent. A contact blocking layer is positioned on an outer surface of the n-type layer that provides electrical isolation of the IBand of the p-type and n-type layers. The contact blocking layer comprises aluminum gallium arsenide and indium gallium phosphide.    USE - Intermediate band solar cell (IBSC) i.e. dilute Group III-V nitride IBSC.    ADVANTAGE - The IBSC includes the a p-n junction based on dilute III-V nitride materials and positions a pair of contact blocking layers on opposite surfaces of the p-n junction for electrically isolating an intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thus increasing open circuit voltage of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC, and increasing the overall power conversion efficiency of the IBSC. The IBSC includes p-n junction absorber layers that have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection. The IBSC includes dilute Group III-V nitride layers and contact blocking layers so as to maximize the solar cell performance and prevent electrons and holes from escaping the layers through conduction in the IBand, so that the open circuit voltage values and the photocurrent generated by light absorption through the isolated IBand are increased, and the single P-N junction is utilized along with contact blocking layers, thus simplifying cell design and lowering production costs. The IBSC includes n-aluminum gallium arsenide blocking layer that is lattice-matched with adjacent layers of the IBSC so as to maximize the overall quality of the material used, thus minimizing any material-based defects that occur from routine usage or testing in the IBSC.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a test structure of an IBSC.    IBSC (100)    Sunlight (401)    Gallium arsenide substrate layer (402)    N-type gallium arsenide layer (406)    Gallium arsenide protective contact layer (412)