High-Efficiency Cu2znsnse4 Solar Cells Prepared by the Selenization of the Electrodeposited Metal Precursor at Low Se-Pressure and Snsex-Vapor Environments

Earth-abundant copper-zinc-tin-chalcogenide kesterites, Cu2ZnSn(S,Se)4, have been examined as most potential alternatives for the leading technologies. However, fabricating low-cost and high-efficiency Cu2ZnSnSe4 (CZTSe) solar cells prepared by electrodeposited metal precursors followed by selenization face several challenges. The first one is how to avoid the impurity incorporation into the metal precursor during electrodeposition and to complete its alloy for better selenization. The next one is how to use a selenization technique with a high temperature at high Se vapor pressure or at low Se vapor pressure with a SnSex vapor to obtain larger grain size and uniform element distribution, and to reduce the formation of the secondary phase and the MoSe2 layer. And the last one is how to reduce the number of recombination centers by the passivation or other techniques to increase the open circuit voltage. In last year, we had proposed a three-year project to solve these problems to achieve a high efficiency CZTSe solar cell. Unfortunately, the project was granted only one year. According to reviewer’s comments, we revise the second and third year of the last year project to one year. In progressing project, we are using the pulse and magnetic assistant electrodeposition to obtain high quality metal precursor. In addition, we also use a Taguchi method to find the optimized annealing parameters to obtain a completed alloy formation. Now, we can obtain an 8.32% efficiency of CZTSe solar cells. In this project, the selenization of metal precursor by using a high temperature at low Se vapor pressure with a SnSex vapor or three step selenization at low Se vapor pressure will be systematically investigated to avoid the formation of binary phases and MoSe2 and to understand formation mechanism of CZTSe thin films. A near chemical equilibrium reaction for the selenization is implemented to avoid the CZTSe decomposition. In order to further improve the film quality, a plasma-assisted activation Se source is used to activate Se molecule for supplying strong Se vapor to participate the reaction. For reducing the defects, the surface defects will be effectively passivated by a plasma-assisted activation sulfur source. In addition, the performance improvement of CZTSe solar cells will be studied by introducing a superficial Ge or K layer in the metal precursor. Through the mentioned-above investigation and based on our previous CZTSe study, we believe that as high as 10 % efficiency of CZTSe solar cells can be achieved.

Project ID:PB10608-2425
External Project ID:MOST106-2221-E182-046