NOVELTY - A non-sintered structure comprises a first non-sintered nanocrystal layer; and a second non-sintered nanocrystal layer. The two layers interact electronically.    USE - Non-sintered structure for solar cell device (claimed) or photovoltaic device.    ADVANTAGE - The non-sintered structure can provide inorganic nanocrystal photovoltaic device that is efficient over a very large portion of the solar spectrum and can be fabricated at low temperature.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a solar cell device (100) comprising a substrate (110) comprising a first conducting layer (140), a copper sulfide nanocrystal layer (120) adjacent the first conducting layer of the substrate, a cadmium sulfide nanocrystal layer (130) adjacent the copper sulfide nanocrystal layer, and a second conducting layer adjacent the cadmium sulfide nanocrystal layer;    (2) a method comprising forming a first non-sintered nanocrystal layer, and forming a second non-sintered nanocrystal layer, where the two layers interact electronically;    (3) a method for making semiconductor nanocrystals, each semiconductor nanocrystal having two elements, comprising mixing a first precursor comprising the second element and an organic solvent to form a first solution; heating the first solution to a first temperature not greater than 140 degrees C; injecting a suspension comprising a second precursor comprising the first element into the first solution to form a second solution; heating the second solution to a second temperature above 140 degrees C; and keeping the second solution at the second temperature long enough for the semiconductor nanocrystals to be formed;    (4) nanocrystals made by the method;    (5) pure monodisperse comprising copper sulfide; and    (6) a method of making copper sulfide nanocrystals comprising mixing ammonium diethyldithiocarbamate with dodecanethiol and oleic acid to form a first solution; heating the first solution to a first temperature not greater than 140 degrees C; injecting a suspension of copper (II) acetylacetonate and oleic acid into the first solution to form a second solution; heating the second solution to a second temperature above 140 degrees C; and keeping the second solution at the second temperature long enough for the copper sulfide nanocrystals to be formed.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram of components in a photovoltaic or solar cell device.    Solar cell device (100)    Substrate (110)    Copper sulfide layer (120)    Cadmium sulfide layer (130)    Conducting layer (140)