New insights in the electrodeposition mechanism of CuInSe₂ thin films for solar cell applications

The electrodeposition of CuInSe₂, one of the most appropriate absorber for thin layer photovoltaic solar cells, is investigated with a rotating disc electrode by voltametry, steady-state polarization and electrochemical impedance spectroscopy in dilute acidic solutions. Three main potential domains are distinguished. At low cathodic polarizations, binary Cu-Se compounds are deposited. Indium starts to incorporate beyond a potential threshold which is associated with a current peak similar to a passivation peak and with impedance diagrams showing a negative polarisation resistance. For more negative potentials the impedance diagrams exhibit mainly characteristic features corresponding to charge transfer under diffusional control. A reaction path is proposed. These results are discussed in terms of general behavior of multinary compound deposition.