High Efficiency Copper Indium Gallium DiSelenide (CIGS) by High Power Impulse Magnetron Sputtering (HIPIMS): A Promising and Scalable Application in Thin-film Photovoltaics

Abstract

A novel method to deposit Copper Indium Gallium Diselenide (CIGS) using High Power Impulse Magnetron Sputtering (HIPIMS) was demonstrated and compared to the existing DC magnetron sputtering process. The metal-ion assisted thin-film growth inherent to a HIPIMS deposition process was used to advantage in depositing CIGS films. The HIPIMS plasma was characterized by measuring ion currents on a Langmuir probe placed into the plasma sufficiently close to the substrate. The high density plasma consisting of both metal and metal ions resulted in CIGS thin-film solar cells of superior conversion efficiencies (˜13%) as compared to conventional DC magnetron sputtering (˜10%). The efficiency enhancement was attributed to the improvement in the shunt resistance of the solar cell which corresponds to the increase in the density of the CIGS layer. Furthermore, it was also possible to grow large grained CIGS (˜1 micron) with high mobility metal-ions from the HIPIMS process. The scalability potential of the HIPIMS CIGS process was also demonstrated by running a 1.5 m long Copper-Indium-Gallium rotatable in a selenium environment using a HIPIMS power supply. The cylindrical magnetron was run at an average power of 7.8 KW and peak powers of as much as 300 KW with controlled arcing. The existence of a HIPIMS plasma was confirmed by the ion currents on the Langmuir probe and the metal signals from a Plasma Emission Monitor (PEM).