Correlation between silver alloying, post-deposition treatment, and photovoltaic parameters in chalcopyrite thin film solar cells produced at low temperature

In this study, the correlation between silver alloying, post-deposition treatment, and photovoltaic parameters in chalcopyrite thin film solar cells produced by multi source physical vapour deposition chamber at low temperature was investigated by scanning electron microscope, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, current density-voltage, and external quantum efficiency measurement techniques. It is found that, the silver alloying increased the average grain size in samples with and without NaF post-deposition treatment while NaF post-deposition treatment did not have a significant effect on average grain size. Silver alloying did not have an important effect on open circuit voltage without NaF post-deposition treatment application. However, NaF post-deposition treatment increased the open circuit voltage value of the reference sample from 598 mV to 628 mV. Moreover, the application of both silver alloying and NaF post-deposition treatment resulted the best open circuit voltage with 658 mV. Both the application of silver alloying and NaF post-deposition treatment separately and the application of both together improved the fill factor and short circuit current density values. The distributions of gallium and indium in the samples became more homogeneous and the solubility of the sodium in the structure was increased after silver alloying. Post-deposition treatment decreased the open circuit voltage deficit and both NaF post-deposition treatment and silver alloying improved the solar cell efficiency. The best efficiency of 16.2% was obtained in the sample with silver alloying and the NaF post-deposition treatment.