NOVELTY - A monolithically interconnected photovoltaic module having cells which are electrically series includes cell isolation diode layer. The diode junction intervenes the substrate and the cell layers in which the absorber and diode interfacial regions are of a same conductivity type orientation. The diode layer has a reverse-breakdown voltage sufficient to prevent inter-cell shunting.    USE - As a monolithically interconnected photovoltaic module.    DETAILED DESCRIPTION - A monolithically interconnected photovoltaic module having cells which are electrically series connected comprises a substrate, and cells formed on the substrate. Each cell includes a primary absorber layer having a light receiving surface and a p-region, formed with a p-type dopant, and an n-region formed with an n-type dopant adjacent the p-region to form a single pn-junction. A cell isolation diode layer has a p-region, formed with a p-type dopant, and an n-region formed with an n-type dopant adjacent the p-region to form a single pn-junction. The diode junction intervenes the substrate and the cell layers in which the absorber and diode interfacial regions are of a same conductivity type orientation. The diode layer has a reverse-breakdown voltage sufficient to prevent inter-cell shunting. Each cell junction is electrically isolated from adjacent cells with a vertical trench through the pn-junction of the diode layer to the substrate. Interconnects are disposed in the trenches contacting the absorber regions of adjacent cells which are doped an opposite conductivity type. Electrical contacts are also provided.    An INDEPENDENT CLAIM is also included for a method of electrical isolation of component cells in monolithically interconnected modules comprising forming a substrate, growing cells on the substrate, electrically isolating each cell from an adjacent cell with a vertical trench through the pn-junction of the diode layer to the substrate, and forming electrical contacts on the cells and interconnecting the absorber regions of adjacent cells which are doped the opposite conductivity type.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of the photovoltaic module, showing series-connected cells formed on cell isolation diodes on a substrate.