Abstract
We have investigated the effect of low-temperature (80oC) post-deposition heat treatment onto CuInTe2 (CIT) thin films prepared by one-step electrochemical technique. Aqueous precursor solution consisting ionic species of Cu, In and Te with pH 4.0 was used for the growth of CIT layers. The deposition potential was optimized using cyclic voltammetry. Conventional three-electrode geometry was used to electrodeposit CIT thin films onto CdS substrates. The structural, optical, morphological, compositional and transport properties were studied with the aid of XRD, Raman, HRTEM, UV-Visible, FESEM, EDAX, I-V and C-V measurements. As-deposited samples were amorphous in nature, however upon heat treatment highly crystalline CIT thin films with tetragonal crystal structure were exhibited. The values of energy band gap for the films deposited at -0.7 V and -0.8 V versus Ag/AgCl were estimated to be in the range 1.02 eV to 1.1 eV. Compact, uniform, void free and well adherent films were deposited at -0.7 V and -0.8 V. The samples were heat treated at 80oC for 60 minutes therefore, visible changes in the surface morphology were not observed by SEM. Indium rich films were electrodeposited for -0.7 V and -0.8 V, however upon heat treatment stoichiometric layers were obtained. Schottky diodes are formed with Au metal contact in all cases. The solar cell investigated under illumination at 1.5 AM exhibits the short circuit current density (Jsc), 40.75 mA/cm2; open circuit voltage (Voc), 255 mV; fill factor (FF), 41% and power conversion efficiency (η), 4.01%. This low-temperature heat treatment procedure could be advantageous for the fabrication of CIT solar cells onto flexible substrates.
Highlights
The ternary chalcopyrite semiconductors are technologically important group of semiconductors because of their photofunctionality
CIT sample deposited at -0.8 V upon subsequent heat treatment exhibited the peak related to tetragonal structure of CIT along with the fluorine doped tin oxide (FTO) peaks, which are marked as solid circle ()
The energy band gap of CIT samples was found to be ~ 1.05 eV and 1.07 eV for the deposited at -0.7 V and -0.8 V, respectively, which was reduced to 0.9 eV to 1.0 eV upon heat treatment
Summary
The ternary chalcopyrite semiconductors are technologically important group of semiconductors because of their photofunctionality. Mise and Nakada [5] have thoroughly studied the effect of substrate temperature and film thickness on properties of CuIn3Te5 thin films prepared by single step co-evaporation. We report the electrodeposition conditions for CIT and the effect of low-temperature heat treatment was thoroughly investigated by various characterization techniques. Potentiostat/ galvanostat Model, Biologic SP 300 was employed to study the cyclic voltammetry (CV) experiment and the electrodeposition of CIT films. The heat treatment experiment at 80°C, was performed onto CIT layers as well as CdS/CIT hetero-structure sole cell device at least 10 different sample to study the repeatability and reproducibility of the results. The dark and illuminated J-V measurements were performed using above potentiostat equipped with necessary software and probe system at light intensity 100 mW cm-2 (AM 1.5)
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