Electrochemical phototvoltaic cells with pulse electrodeposited copper indium selenide films

CuInSe₂ (CIS) is a direct band gap semiconductor, whose band gap can be varied from 0.95 eV to 1.04 eV depending on the preparation condition and environment. CIS materials are one of the best absorber materials for use in solar cells due to its high optical absorption coefficient. CIS films were deposited on tin oxide coated glass substrates ( 5 ohm/ sq) at different duty cycles in the range of 6 50 %. Three well defined characteristic peaks at 26.6°, 44.1° and 52.4° were observed in the x-ray diffraction pattern. Composition of the films was estimated from the EDAX spectrum possessed Cu/In ratio of 1.01. The energy band gap is lower than that of 1.04 eV. The surface roughness increased from 0.25 nm to 1.0 nm with duty cycle. As the duty cycle increases, the resistivity increases from 1.0 ohm cm to 10 ohm cm. Photoelectrochemical cell studies were made in 1M Polysulphide (1M S, 1M NaOH, 1M Na₂S) redox electrolyte. Films deposited at 50 % duty cycle have exhibited maximum power output of 0.625 V and 16 mA cm^-2 at 60 mW cm^-2 white light illumination. Effect of photoetching and capacitance voltage studies were made. The films exhibited p-type behaviour.