Electrodeposition of selenium, indium and copper in an air- and water-stable ionic liquid at variable temperatures

The electrochemical behaviour of Au(1 1 1) and highly oriented pyrolytic graphite (HOPG) substrates in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP]Tf2N) was investigated using in situ scanning tunneling microscopy (STM). Furthermore, the electrodeposition of Se, In and Cu in the same ionic liquid was investigated. The high thermal stability as well as the large electrochemical window of this ionic liquid compared with aqueous electrolytes allow the direct electrodeposition of grey selenium, indium and copper at variable temperatures, as the first step in making CIS solar cells electrochemically, in a one pot reaction. The results show that grey selenium can be obtained at temperatures ≥100 °C. XRD patterns of the electrodeposit obtained at 100 °C show the characteristic peaks of crystalline grey selenium. Nanocrystalline indium with grain sizes between 100 and 200 nm was formed in the employed ionic liquid, containing 0.1 M InCl3, at room temperature. It was also found that copper(I) species can be introduced into the ionic liquid [BMP]Tf2N by anodic dissolution of a copper electrode and nanocrystalline copper with an average crystallite size of about 50 nm was obtained without additives in the resulting electrolyte.