TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The hydrazine-coordinated In chalcogenide complex is obtained by: adding In or In2Se3 and a chalcogen to hydrazine to obtain a crude product; extracting the crude product with dimethyl sulfoxide; and adding an alcohol solvent to the resulting solution. The hydrazine-coordinated Ga chalcogenide complex is obtained by: adding Ga and a chalcogen to hydrazine to obtain a crude product; extracting the crude product with dimethyl sulfoxide; and adding an alcohol solvent to the resulting solution. The chalcogen is sulfur or selenium. EXAMPLE - A coating solution (test) for forming a light-absorbing layer was produced as follows: a Cu metal (383.0 mg) and 4 equivalents of Se (1903.2 mg) were added to DMSO (10 ml) having 2 equivalent (per 1 equivalent of Cu metal) of hydrazine anhydride (378 mu l) added to it, and stirred for 3 days to dissolve the added contents. Then, the remaining hydrazine was removed from the resulting solution while flowing nitrogen, and the solution was then subjected to filtration using a 0.2 mu m polytetrafluoroethylene (PTFE) filter. Isopropyl alcohol (IPA) (total of 20 ml) was gradually added to the filtrate to perform recrystallization, thereby obtaining a black hydrazine-coordinated Cu-Se chalcogenide complex (2424 mg). Separately from the above, indium selenide (964.9 mg) and 1 equivalent of Se (1645.2 mg) were added to hydrazine anhydride (5 ml), followed by stirring at room temperature for 3 days. Then, the remaining hydrazine was removed from the resulting solution while flowing nitrogen to obtain crude product. The crude product was extracted with DMSO, and the extraction solution was subjected to filtration using a 0.2 mu m PTFE filter, followed by concentration. IPA was added to the concentrated solution, followed by stirring to precipitate a dark-red product. Then, supernatant was removed, and the precipitate was washed with IPA and dried, thereby obtaining a dark-red hydrazine-coordinated In-Se chalcogenide complex (838.2 mg). Separately from the above, a Ga metal (418.3 mg) and 2 equivalents of Se (947.5 mg) were added to hydrazine anhydride (5 ml), followed by stirring at room temperature for 1 week. Then, the remaining hydrazine was removed from the resulting solution while flowing nitrogen to obtain a crude product. Subsequently, the crude product was extracted with DMSO, and the extraction solution was subjected to filtration using a 0.2 mu m PTFE filter, followed by concentration. IPA (20 ml) was added to the concentrated solution, followed by stirring to precipitate a brownish product. Then, supernatant was removed, and the precipitate was washed with IPA and dried, thereby obtaining a dark-brown hydrazine-coordinated Ga-Se chalcogenide complex (428.7 mg). The hydrazine-coordinated Cu-Se complex, the hydrazine-coordinated In-Se complex and the hydrazine-coordinated Ga-Se complex were dissolved in DMSO to produce a coating solution for forming a light-absorbing layer. The coating solution was adjusted to a CIGS/DMSO solution having a concentration of 0.3 mol/l, and the mixing molar ratio was adjusted to Cu/(In+Ga) of 0.92, In/(In+Ga) of 0.72, and Ga/(In+Ga) of 0.28. The amount of Sb was adjusted to Sb/(Cu+In+Ga)x 100 of 0.1 mol%, and the amount of Na was adjusted to Na/(Cu+In+Ga)x 100 of 0.05 mol%. Application of the coating solution was performed by a spin-coating method, and the baking was performed by conducting a soft bake at 300 degrees C for 5 minutes, followed by annealing at 540 degrees C for 5 minutes. A solar cell was produced so that Mo layer, a CIGS layer (light-absorbing layer), a CdS layer, i-ZnO layer, an ITO layer, an Al layer, Ni layer and an MgF2 layer were laminated on a substrate in this order. In control method, a hydrazine-coordinated Cu-Se complex, a hydrazine-coordinated In-Se complex and a hydrazine-coordinated Ga-Se complex were obtained as crude products without performing re-precipitation or recrystallization. The crude products were dissolved in a DMSO solution having monoethanolamine added to it, thereby obtaining a coating solution for forming a light-absorbing layer. The coating solution was adjusted to CIGS-DMSO/monoethanolamine solution (3:1) having a concentration of 0.1 mol/l, and the mixing molar ratio was adjusted to Cu/(In+Ga) of 0.92, In/(In+Ga) of 0.72, and Ga/(In+Ga) of 0.28. Application of the coating solution was performed by spin-coating method, and the baking was performed by conducting a soft bake at 170 degrees C for 5 minutes, a further soft bake at 190 degrees C for 5 minutes, followed by annealing at 490 degrees C for 30 minutes. A solar cell was produced so that Mo layer, a CIGS layer (light-absorbing layer), a CdS layer, i-ZnO layer, an ITO layer, an Al layer, Ni layer and an MgF2 layer were laminated on a substrate in this order. The test/control solar cells were evaluated for conversion efficiency, fill factor (FF), and open circuit voltage (Voc). The results for test/control were: conversion efficiency (%) = 6.03/0.21; FF (%) = 56.5/36.7; and Voc (mV) = 417/0.193.