NOVELTY - The device has a vertical solar cell chip (2) received in a groove on a first primary surface of a base solar cell chip (1) to form a vertical plane with respect to a horizontal plane defined by the first primary surface of the base solar cell chip. The vertical solar cell chip includes a first primary surface and a second primary surface opposite to the first primary surface of the vertical solar cell chip. The base solar cell chip includes a second primary surface opposite to the first primary surface of the base solar cell chip.    USE - Three-dimensional (3-D) solar cell device for a concentrated photovoltaic solar cell system (claimed) for collecting sunlight from a sun position for household hot-water applications.    ADVANTAGE - The device generates thermal and electrical solar energy from solar radiation using a 3-D solar cell design structure without a sun-tracking system and utilizes liquid cooling to provide maximum energy utilization from the thermal and electrical solar energy. The device captures sunlight from the position of the sun without tracking sun's movement and without using a solar tracking system by using corner-cube configuration to compensate for latitudinal and longitudinal changes due to seasonal and daily solar movements, thus improving long term reliability and reducing cost of the system. The device is incorporated with a liquid cooling channel at a back of solar cells such that maximum solar intensity can be used for generating solar electricity.    DETAILED DESCRIPTION - The base solar cell chip comprises multi-junction III-V solar cell material. The groove is a V-notch groove or rectangular-channel groove. An INDEPENDENT CLAIM is also included for a concentrated photovoltaic solar cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a concentrated photovoltaic solar cell system using a 3-D solar cell device.    Base solar cell chip (1)    Vertical solar cell chip (2)    Input port (5)    Dome (11)    Focusing lenses (11A, 11B)