NOVELTY - A low energy gap nanocrystal semiconductor light anode film is prepared by adding titanium salt to hydrochloric acid solution to prepare metal salt solution, adding metal salt solution into surface active agent, setting and aging, and drying to obtain nanotitanium dioxide powder doped with metal; preparing nanotitanium dioxide sol doped with metal; painting sol on base of conducting glass and obtaining conducting glass painted with sol; and putting nanotitanium dioxide powder and sol in mortar box to obtain sizing agent, and painting sizing agent on conducting glass.    USE - Method for preparing low energy gap nanocrystal semiconductor light anode film (claimed) for solar cell.    ADVANTAGE - The method provides anode film doped with metal, which improves solar utility ratio and energy level matching performance of the light anode film and a dye molecule, improves Femi energy level of anode material of titanium dioxide and open-circuit voltage, and improves photoelectric converting performance of cell and photoelectric converting efficiency of solar cell.    DETAILED DESCRIPTION - Preparing low energy gap nanocrystal semiconductor light anode film doped with metal comprises:    (A) adding titanium salt to hydrochloric acid solution with 1-4M of titanium salt to prepare metal salt solution, a mole ratio of titanium salt and metal salt is 100:0.5-5, dropwise adding the metal salt solution and surface active agent, adding precipitating agent until the pH value is 6-9, setting and aging for 24 hours, centrifugal cleaning 4 times with de-ionized water and then with absolute ethyl alcohol, drying at 50 degrees C for 48 hours, calcining at 500 degrees C for 1 hour, and obtaining nanotitanium dioxide powder (A) doped with metal;    (B) taking hydrochloric acid aqueous solution of titanium salt and adding absolute ethyl alcohol, adding metal salt solution, a mole ratio of titanium salt and metal salt is 100:0.5-5, mixing for 2 hours, and obtaining nanotitanium dioxide sol (B) doped with metal;    (C) painting sol (B) on base of conducting glass and controlling thickness at 20-100 nm, calcining at 450 degrees C for 0.5 hour after drying, and obtaining conducting glass (C) painted with sol (B);    (D) putting powder (A) and sol (B) in mortar box, obtaining sizing agent after milling for 30 minutes, painting the sizing agent on the conducting glass (C), controlling thickness at 5-20 nm, calcining at 450 degrees C for 0.5 hour after drying, and obtaining titanium dioxide nanocrystal semiconductor light anode film doped with metal (D); and    (E) steeping semiconductor film (D) in ethanol solution of 4,4-ruthenium dicarboxybipyridine for 12 hours, cleaning with absolute ethyl alcohol after taking out, drying by nitrogen, and obtaining the low energy gap nanocrystal semiconductor light anode film doped with metal (E).