The Preparation Of CuInSe₂ Material And Thin Film

Solar energy is one kind reproducible clean energy. For the serious energy crisis, it is significant to research solar cells. In the low-cost second generation solar cells, Cu(In,Ga)Se₂ (CIGS) thin films solar cells has a high theory conversion efficiency (30 %), and it very stable, so research of it intrigues people very much. So far the world highest conversion efficiency of this cell had reached 19.9 %. For preparing high quality chalcopyrite Cu(In,Ga)Se2 or CuInSe₂ thin films by selenization, we should well understand the theory and process of the recrystallization occurring in selenization. For this reason, we did two experiment to dicuss the recrystallization of CuInSe₂, as follow:(1) we evaporated and prepared InSe/Cu bilayer as the precusor layer, and selenized the precusor in graphite box using selenium as the source. From analysing the phase change after selenizing in different temperature, the machanism of chalcopyrite CuInSe₂ formation was obtained. But the prepared CuInSe₂ film was bilayer and there was a interlayer between the bilyer. This interlayer was CuIn3Se5 or In-rich CuInSe₂ layer. Three methods were used to remove the interlayer and bilayer structure, as follow: One, using Br-MeOH etching follwed by KCN etching, we removed the interlayer and upper layer; Two, when prepared precusor layer, putting In₂Se₃ and Cu source on the boat at the same time, this eliminated the influence of the gas which adhered to the InSe layer when we open the cavity to put copper source; Three, increasing the Se vapour pressure, this maintained the Se-rich Cu-Se compounds during selenization, and promoted the crystallization of CuInSe₂. The third method waste less material, and remove the interlayer and bilayer structure.(2) Chalcopyriteα-CuInSe₂ (CIS) was prepared from mechanically alloyed powders of Cu₂Se and In₂Se₃ selenides. The mechanical alloying technique produced an amorphous-like mixed powders of (Cu₂Se)_x(In₂Se₃)_1-x, Cu₃Se₂, Cu₂Se, and InSe.α-CuInSe₂ formed essentially at a temperature at ³50℃in both the Se- and the non-Se environments. In the non-Se environment, reactions occurred by a solid-solid reaction and a certain amount of Se was released from the mixed powder, resulting in small-grained, Se-deficient, and poor crystallineα-CuInSe₂ powders. When annealed in the Se environment, reactions occurred by a liquid-solid reaction above 450℃. Large-grained and good crystalline quality of chalcopyrite CIS with near stoichiometric atomic ratio was obtained above 450℃.