TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The preparation of the indium sulfide buffer layer comprises placing conductive glass of titanium oxide nanorod in aqueous solution of indium chloride, thioacetamide and acetic acid to soak for 0.5-4 hours at 50-80 degrees C, where the concentration of the indium chloride is 0.02-0.05 mol/l and molar ratio of indium chloride, thioacetamide to acetic acid is 1:(2-4):(2-4). The preparation of the metal counter electrode is vacuum thermal evaporation or sputtering. The preparation of the tribasic/tetrabasic sulfur compound nanocrystal comprises: (i) preparing copper oleate or silver nitrate, indium oleate and oleyl amine solvent in a reaction container to prepare solution; (ii) adding oleyl amine solution of sulfur powder and/or selenium powder to the solution; (iii) under argon or nitrogen protection condition, agitating the mixed solution for 0.5-4 hours at 120-200 degrees C; and (iv) naturally cooling to room temperature, precipitating, washing and drying to obtain product. The preparation of the titanium dioxide nanorod array comprises: uniformly mixing hydrochloric acid and titanium source in a reaction kettle, and placing them in conductive glass; sealing the reaction kettle and reacting for 1-12 hours at 120-200 degrees C; and naturally cooling to room temperature, washing, drying and calcining to obtain product. Preferred Components: An indium sulfide buffer layer is arranged between the titanium dioxide nanorod array and tribasic/tetrabasic sulfur compound nanocrystal light absorbing layer. The organic solvent is toluene, xylol, chlorobenzene or dichlorobenzene. The concentration of the sulfur compound nanocrystal in the organic solvent is 0.01-0.2 mol/l. The molar ratio of copper oleate or silver nitrate, indium oleate, sulfur powder and selenium powder is 1:1:x:(2-x), where x is 0-2. In the step (i), the concentration of oleyl amine in indium oleate is 0.2-1 mol/l. In the step (ii), the concentration of the sulfur powder and/or selenium powder in oleyl amine is 0.02-0.2 mol/l. The concentration of hydrochloric acid is 4-10 mol/l. The titanium source is tetrabutyl titanate or tetraisopropyl titanate and its volume content is 1-5%. The calcining atmosphere is air or oxygen having a temperature of 300-500 degrees C.