Because of the attractive performances of CIGS (Cu(In,Ga)Se₂) type solar cell, various researchers tried to synthesis of it by using gas phase method or liquid phase reduction method in organic solvents. In the case of former, productivity is relatively low, since vaporizing temperature of three or more elements is extremely different, which read the large amount of waste of resources, nevertheless synthesized solar cell shows the high performances.

So, later methods were vigorously researched since it is ecological and also economical technique. For example, Ye et al. synthesized Cu-In alloy particles by using chemical reduction method in organic solvent and the Cu-In alloy precursor films were transformed to CuInSe₂ films by selenization [1]. The resulting cells demonstrate a maximum energy conversion efficiency of 3.92 %. However, total cost of this method is not low since organic solvent should be used.

Therefore, we tried to synthesized uniform Cu-In (CI) alloy nanoparticles by using restrict controlling method of metallic complexes in an aqueous solution under room temperature [2]. In this method, reduction potential of the metal species can be controlled under the room temperature, consequently alloy nano materials with uniform and well crystallized structure can be successfully synthesized.

　　Therefore, in this study, to synthesize Cu-In-Ga (CIG) nanoparticles, aqueous phase Ga doping method to Cu-In (CI) alloy precursor materials were researched.

     Condition of Ga, Cu and In complex were calculated by using critical stability constants. Reduction potential of homogenized metal complex were analyzed by using cyclic voltammetry. Ga doped CI alloy nanoparticles were synthesized by using chemical reduction method under ambient conditions using metal chlorides as metal sources and sodium borohydride as a reducing agent.

By obeying to these calculation results and also electrochemical potential measurement, CI nanoparticles can be successfully synthesized in aqueous solution under room temperature. CuIn and also Cu₂In ally nanoparticles can be synthesized.

XRD and SEM/EDX measurement demonstrated that Ga can be doped into CI nanoparticles, and doping ratio of Ga into CI nanoparticles were depended on the reduction rate and also reduction method. For example, maximum Ga concentration in CIG nanoparticles were reached c.a. 20% when the molar ratio of reducing agent against to metals reached to ten. Moreover, these results shows that reduction procedure was seriously affected to the doping ratio of Ga.

Another detailed results will be presented in our session.

This work has been supported by the Grant-in-Aid for Scientific Research (B) (No. 26281054).

 [1] Ye Seul Lim, et.,al, J. Phys. Chem. C, 2013, 117 (23), pp 11930–11940, [2] H. Takahashi et.,al, Applied Catalysis A: General 392 (2011) 80–85.