Post-deposition treatment of Cu2ZnSnSe4 with alkalis

Publication date: Available online 14 November 2016
Source:Thin Solid Films
Author(s): G. Rey, F. Babbe, T.P. Weiss, H. Elanzeery, M. Melchiorre, N. Valle, B. El Adib, S. Siebentritt
Low temperature post-deposition treatment of Cu2ZnSnSe4 with NaF and KF significantly improved the solar cell efficiency (from 6.4% to 7.8% and 7.7% on average, respectively) due to enhanced fill factor (from 0.58 to 0.61 and 0.62), open-circuit voltage (V oc ) (from 314mV to 337mV and 325mV) and short-circuit current density (from 35.3mA⋅cm ⁻² to 38.3mA⋅cm ⁻² and 38.6mA⋅cm ⁻²). V oc improvement was higher for solar cells with NaF treatment due to an increase in radiative efficiency at room temperature and shallower defect activation energy as determined by photoluminescence (PL) and temperature dependent admittance spectroscopy, respectively. In the case of KF treatment, red-shift of the PL, higher band tail density of state and donor activation energy deeper in the band gap were limiting further improvement of the V oc compared to NaF treatment.