NOVELTY - Copper indium aluminum diselenide photovoltaic semiconductor nanocrystal is claimed. The nanocrystal is obtained by solvent thermal method, comprising: (i) mixing copper, indium and aluminum element sources in the organic solvent and reacting under the protection of an inert gas to obtain a solution A; (ii) heating the solution A, adding sulfur element source and/or selenium element source to react, adjusting indium/aluminum ratio and/or sulfur/selenium ratio to adjust the band gap width, matching the band gap width of the material with the optical spectrum of the sun; and (iii) purifying.    USE - The photovoltaic semiconductor nanocrystal is useful in solar battery and near infrared laser (all claimed).    ADVANTAGE - The nanocrystal controls the shape of the nano particle and dimension to adjust the band gap width by adjusting the indium/aluminum ratio and/or sulfur/selenium ratio, so that the band gap width of the material is better matched with the optical spectrum of the sun.    DETAILED DESCRIPTION - Copper indium aluminum diselenide photovoltaic semiconductor nanocrystal is claimed. The nanocrystal is obtained by solvent thermal method, comprising: (i) mixing copper, indium and aluminum element sources in the organic solvent and reacting under the protection of an inert gas to obtain a solution A; (ii) heating the solution A, adding a sulfur element source and/or a selenium element source to react, adjusting indium/aluminum ratio and/or sulfur/selenium ratio to adjust the band gap width, matching the band gap width of the material with the optical spectrum of the sun; and (iii) purifying by adding benzene to disperse and adding alcohol to settle to obtain the target product copper (indium, aluminum) disulfide, copper (indium aluminum) diselenide or copper (indium, aluminum) disulfide diselenide photovoltaic semiconductor nanocrystal. An INDEPENDENT CLAIM is also included for preparing the copper indium aluminum diselenide photovoltaic semiconductor nanocrystal by solvent thermal method, comprising: (i) mixing copper, indium and aluminum element sources in an organic solvent, reacting under the protection of an inert gas at 80-140?Oc to obtain a solution A; (ii) heating the solution A at 200-250 degrees C, adding a sulfur element source and/or a selenium element source to react, adjusting indium/aluminum ratio and/or sulfur/selenium ratio to adjust the band gap width, matching the band gap width of the material with the optical spectrum of the sun; and (iii) adding benzene to disperse, and adding alcohol to settle to obtain the target product copper (indium, aluminum) disulfide, copper (indium aluminum) diselenide or copper (indium, aluminum) disulfide diselenide photovoltaic semiconductor nanocrystal.