NOVELTY - The micron/sub-micron gap thermo-photovoltaic chip structure comprises a photovoltaic cell substrate (1), micron/sub-micron gap spaced from a juxtaposed heat or infrared radiation-emitting substrate and with a radiation-transparent intermediate window material substrate (3) adhered to the photovoltaic cell substrate and bounding the gap space. The thermo-photovoltaic chip structure is enclosed in an evacuated housing. The adherence is effected with an adhesive layer (4) attaching the window surface outside the gap space to the photovoltaic cell.    USE - Used as a micron/sub-micron gap thermo-photovoltaic chip structure.    ADVANTAGE - The micron/sub-micron gap thermo-photovoltaic chip structure has good surface roughness and overall flatness, and can be easily and economically manufactured without thermal mismatch.    DETAILED DESCRIPTION - The micron/sub-micron gap thermo-photovoltaic chip structure comprises a photovoltaic cell substrate (1), micron/sub-micron gap spaced from a juxtaposed heat or infrared radiation-emitting substrate and with a radiation-transparent intermediate window material substrate (3) adhered to the photovoltaic cell substrate and bounding the gap space. The thermo-photovoltaic chip structure is enclosed in an evacuated housing. The adherence is effected with an adhesive layer (4) attaching the window surface outside the gap space to the photovoltaic cell. The window material has a band gap larger than the infrared (greater than 1 electron-volt) and a low density of free carriers or defects, and exhibits refractive index equal to or larger than that of the emitting and photovoltaic cell substrates. The adhesion is free of voids, cracks or delamination. The adhesive layer has a refractive index of greater than 1.4, and high transmission in the infrared. The material of the adhesion layer exhibits compliancy, and consists of epoxies, filled elastomers and solder glasses including lead oxide and chalcogenide glasses. The adhesive material serves a further function of enabling up-conversion of incoming photons. Rare earth ions or compounds or quantum dots are introduced into the adhesive material to enable such up-conversion. The photovoltaic cells are attached to a common window. An INDEPENDENT CLAIM is included for a method of adjusting the uniformity of the gap spacing.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a micron/sub-micron gap thermo-photovoltaic chip structure.    Photovoltaic cell (1)    Substrate (2)    Window material (3)    Adhesive layer. (4)