Photo-electrochemical performance of CIS and CIGS solar thin films arranged through a novel CISe/Ga-Se bilayer electrodeposition

Abstract

In current work, we focused on the electrodeposition of CuInSe2 and CuIn1-xGaxSe2 by a unique two-step deposition method. Initially by a single step technique, CuInSe2 thin film was electrodeposited using an electrolyte comprised of citric acid-SDS. Further, the gallium selenium thin film was deposited on FTO substrate by potentiostatic method in tartaric electrolyte bath to get a bilayer of Ga-Se upon CISe thin film. For improving the adhesion and smoothness of electrolyth bath, sodium dodecyle sulfate has been added and it is also eliminating multinuclear growth. The CISe and CIGSe samples were further annealed at 300 0C and 525 0C in nitrogen atmosphere respectively. The structural, compositional, optical and electronic representation of as electrodeposited and annealed thin films of CISe and CIGSe were investigated by XRD, SEM and electrochemical analysis. The thin film of as electrodeposited and annealed CIS and CIGS exhibited a p-type behavior as confirmed by with photoelectrochemical (PEC) properties and by Mott-Schottky (M−S) test. By the slope and intercept values of the M−S plot, the carrier concentration and flat band values were determined. The calculated carrier concentration of as deposited and annealed CISe and CIGSe thin films are 3.70 × 1023 cm−3, 1.51 × 1024 cm−3, 9.60 × 1021 cm−3 and 7.79 × 1023 cm−3 respectively. The calculated flat band potential of as electrodeposited and annealed CISe and CIGSe thin films are 115 mV,85.48 mV, 332 mV and 58.65 mV. Here also we have done the Electrochemical Impedance Studies (EIS). The EIS were performed for as-electrodeposited and annealed CIS and CIGS thin films in the electrolyte solution to understand the charge transfer mechanism. The observed Rct values 1397 and 178.4 Ω cm2 for as-deposited and annealed CIS film and Rct values 158.2 and 81.27 Ω cm2 for as-electrodeposited and annealed CIGS thin films respectively. At a potential of −0.4 V/SCE, the obtained photocurrent density for as deposited and annealed CISe and CIGSe thin films by PEC test are 1.10 × 10−4 A cm−2, 1.35 × 10−4 A cm−2, 1.07 × 10−4 A cm−2 and 3.01 × 10−4 A cm−2 respectively.