CHEMICAL-REACTION PROCESSES IN SYNTHESIZING CUINSE2 FROM THE ELEMENTS BY THE MELTING METHOD

Chemical reaction processes in synthesizing CuInSe2 from the elements are investigated. The powder method of X-ray diffraction has been used to identify the reaction products formed in increasing temperature. Copper is selenized first to be Cu3Se2. Heated further, the Cu3Se2 changes gradually to another copper selenide which is supposed to be Cu7Se4. On the other hand, an indium selenide formed in an indium-deficient part inside the reaction tube is confirmed to be In6Se7, while in an indium-rich part, it is presumably In2Se. Above 500-degrees-C, the main body of CuInSe2 begins to be formed from Cu7Se4 as the basis. Cu3Se2 which has not participated in forming CuInSe2 begins to diffuse above 500-degrees-C, which is one of the main problems for the stoichiometric control of CuInSe2. The diffused copper selenide also changes to CuInSe2 by absorbing In6Se7 above 600-degrees-C.