Highly dense and crystalline CuInSe2 thin films prepared by single bath electrochemical deposition

Chalcopyrite CIS or CIGS have been regarded as promising absorbing materials for thin-film solar cells with widespread commercialization prospects. The most critical material properties of a CIS absorption layer that affect the overall PV performance include its microstructure and composition at a given bandgap energy. In this study, dense CISe films with high crystallinity and uniform, flat surfaces were fabricated on In2Se3/ITO employing single bath electrochemical deposition by adjusting the deposition parameters, such as the precursor concentration, pH, and applied potential. A simple formula is presented based on Faraday's law to quantitatively estimate the density of the electrodeposited thin films; from this, it was found that the as-deposited films had a very high relative density of 0.73. The high green density of the as-deposited film led to the full densification of the CISe film with ca. 10 μm sized grains. The binary selenide phase remaining in the sintered film was subsequently etched out using a KCN solution, resulting in an overall Cu-deficient composition in the film of [Cu]/[In] = 0.95.

► Optimum conditions for single bath electrodeposition of CuInSe2 were provided.
► In2Se3 was also electrodeposited on ITO for potential use in superstrate-type solar cell.
► Highly dense and crystalline CuInSe2 film was fabricated with Cu-poor composition.
► Semi-quantitative method was presented to estimate the density of electrodeposited film.