Investigation of sodium effects on CIGS thin films deposited by sputtering from a single quaternary

We investigated sodium effects on Cu(In,Ga)Se₂ thin films deposited by sputtering from a single quaternary target without any further post-selenization or sulfurization. We conducted current-voltage measurement to gather device output parameters. We then used capacitance spectroscopy including capacitance-voltage measurement, admittance spectroscopy, and drive-level capacitance profile to investigate sodium effects in our system. Photoluminescence measurement was made to analyze radiative recombination between energy levels. In addition, we used electron probe x-ray analyzer to analyze atomic composition of CIGS thin film. With the help of the techniques mentioned above, we came to a conclusion that sodium behaves as a catalyzer for oxygen atoms to neutralize selenium vacancies.