Doping of Cu2ZnSnSe4 solar cells with Na+ or K+ alkali ions

Abstract

In this work, the addition of molar concentrations of Na⁺ and/or K⁺ in the form of fluorides during the processing of Cu₂ZnSnSe₄ absorber layers was investigated. The beneficial effect of alkali salts on the performance of CZTSe solar cells has been demonstrated through physical and electrical characterization. A maximum power conversion efficiency of 8.3% has been obtained through controlled addition of Na⁺ and K⁺ in the CZTSe absorber as opposed to 6.7% from uncontrolled addition of both. The open circuit voltage in both cases was very much the same but the devices with controlled addition showed lower p-type doping, a low density of charged defects and less band tailing compared to the rest.