Solar cell. [array of cell on common substrate]

An improved solar cell designed for optimum efficiency is comprised of a plurality of series connected unit solar cells formed from a common substrate of semiconductor material. Each unit solar cell has spaced elongate sidewalls, and a dead space area between adjoining sidewalls of adjacent units is made substantially smaller than an active, light receiving area, extending between the opposite sidewalls of each individual unit. In addition, the width of the active area is concisely limited to ensure that radiation incident on the active area is incident at a point which is spaced from the p-n junction of each unit by no more than a predetermined optimum distance. Reducing the dead space area while concisely limiting the width of the active area provides improved solar cell performance without requiring focusing lenses.