Electrodeposition of CIS films on the Mo back electrodes with different crystallinities

Electrodeposition of copper indium diselenide (CuInSe2), which is an absorption layer for thin film solar cells, has been studied on a molybdenum (Mo)-coated glass with different crystallinities. Metastable FCC Mo and BCC Mo coatings were prepared by R.F. sputtering with varying R.F. power (100–170 W) and Ar pressure (3–11 mTorr). Experimental results indicated that the Mo coating deposited at lower power and higher pressure had smaller crystallite size. Cross-sectional transmission electron microscopy showed that the Mo coating deficient in crystallinities contained micro voids residing in the boundaries of the columnar grains and had higher oxygen content, as measured by energy dispersive spectroscopy. The crystallinity of Mo coatings strongly influenced the open circuit potential in the electrolyte for CIS electrodeposition. Consequently, the Cu/In ratio of CIS deposits plated at a constant potential (−0.7 vs. SCE) varied with the distinct Mo coatings. Moreover, the CIS deposit on the various Mo-coated glasses displayed a different morphology. The effect of the crystallinity of Mo coatings on hydrogen evolution reaction at pH 1.55 was also explored. Hydrogen evolution during the CIS electrodeposition may be one of the key factors to influence the CIS morphology. How the crystallinity of the Mo coating affects the composition and morphology of the CIS deposits can be useful for device fabrication and deserves for further study.

► The sputtering power and Ar pressure influence the structure of R.F. sputtered Mo.
► The structure of Mo coatings determines the integrity of electrodeposited CIS.
► The Mo coating with higher oxygen and higher electric resistivity has a lower HER.
► Compact, coarse-grained CIS is deposited on the Mo coating with a lower HER.