Defect characterization in co-evaporated Cu2ZnSnSe4 thin film solar cell

• Defect states in Cu2ZnSnSe4 thin film solar cell was investigated.
• Two acceptor levels were measured from temperature dependent C-V measurements.
• One defect signal was observed from admittance spectroscopy.
• The effects of these defects on the solar cell were discussed.

Cu2ZnSnSe4 (CZTSe) solar cell fabricated by selenization of co-evaporated Cu–Zn–Sn–Se precursor thin film exhibited 6.2% conversion efficiency. Defects in the solar cell were investigated by temperature-dependent capacitance-voltage and admittance spectroscopy. Capacitance-voltage measurements showed that the p-type conductivity of CZTSe absorber layer was mainly attributed to two acceptor levels with activation energy of 0.02 eV and 0.11 eV. The admittance spectra exhibited capacitance steps that might have originated from a defect level with activation energy of 0.16 eV. The effects of these defects on the solar cell were discussed.