Polyaniline (PANI) thin films have been electrochemically synthesized onto conducting glass substrates. The current study demonstrates that the properties of PANI films depend on the concentration of dopant acid. Well-adherent PANI coatings were obtained under potentiodynamic conditions during sequential scanning of the potential region between −0.35 V and +1.7 V with respect to silver/silver chloride. The structural, optical, and morphological properties of PANI films were studied with the aid of X-ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and field-emission scanning electron microscopy (FESEM). Current–voltage ( I- V) measurements were performed to study the electrical properties of PANI films. The XRD peaks observed at 2 θ = 15.4°, 24.2°, and 25.1° confirm the synthesis of emeraldine form of PANI. The strong absorption peaks observed in the UV-Vis absorption spectra at 317 nm (π–π* interband transition), 371–427 nm (polaron band transition), and 750 nm (bipolaron band transition) confirm the formation of emeraldine oxidation state of PANI. A broad peak attributed in the PL spectra around 395 nm is related to the transition from polaronic band to the π band. All the intense bands attributed in the Raman spectra are associated with the emeraldine oxidation state of PANI. FESEM images reveal the formation of fibers and belts of PANI. Highly conducting thin films of PANI deposited at higher concentrations of dopant acid were confirmed by I- V measurements.

Electrodeposition of Cu­(In,Ga)­Se2 (CIGS) thin film is an attractive approach for the development of highly efficient low-cost solar cells. This work focuses on the effects of various electrodeposition parameters on the growth and properties of CIGS layers. The films deposited at −0.9 V tend to drive the growth of CIGS favoring (112) crystal orientation, whereas the films deposited at −1.6 V show the orientation along (220)/(204). Interplanar distances corresponding to (112) and (204/220) planes could be observed in the high resolution transmission electron microscopy (HRTEM) images of the respective films, confirming the dependence of the texture on the deposition potential. Films with larger grains could be grown by maintaining higher temperature (130 °C) during the deposition of layers. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Cu+, In3+, Ga3+, and Se2– valence states in the CIGS layers prepared at −0.9 and −1.6 V. The film deposited at −1.6 V with (220/204) orientation showed high efficiency as compared to the film deposited at −0.9 V with (112) orientation. The observed solar cell parameters, measured under illuminated condition of input power intensity 100 mW/cm2, were V OC = 0.357 V; J SC = 27 mA/cm2, FF = 44, and η = 4.90; and V OC = 0.460 V, J SC = 34 mA/cm2, FF = 58, and η = 9.07 for the deposition potentials of −0.9 and −1.6 V, respectively.

Polycrystalline CuInSe2 (CIS) thin films have been prepared by low-cost electrochemical method from non-aqueous ethylene glycol solvent onto cadmium sulfide (CdS) thin films. The codeposition potential for Cu, In and Se was optimized with cyclic voltammetry measurements. CIS layers were electrodeposited at -1.1, -1.3 and -1.5 V versus Ag/AgCl references in air-tight custom made electrodeposition cell. The films were selenized at 400 °C for 20 minutes. The optical, structural, morphological, compositional and optoelectronic properties of as-prepared and selenized samples were studied using UV-Vis spectrophotometer, X-ray diffractometer, Transmission electron microscopy (TEM), Scanning electron microscope (SEM), Energy dispersive x-ray analysis (EDAX) and current-voltage (I-V) measurements. Three prominent sharp peaks of tetragonal CIS, (112), (204)/(220), and (312/116) were revealed in all asprepared and selenized samples. Upon selenization the crystallinity of the samples was found to be improved remarkably. Compact, void free, and nearly uniform thin films of grain size ~ 1 µm were deposited. The as-deposited and selenized CIS samples were Cu-rich whereas the contents of Se was ~ 50% obtained by EDAX analysis. The value of inter-planer distance, d = 3.339 Å was measured by HRTEM corresponds to (112) plane of tetragonal CIS crystal structure. The circular spotted rings observed in selected area diffraction (SAD) pattern were confirmed (112), (204)/(220) and (312)/(116) reflections of CIS. The solar cell parameters, Voc, Jsc, FF and efficiency were found to be 303 mV, 28 mA/cm 2 and FF ~ 53 % and η = 4.5 % for the CIS film deposited at -1.5 V. The values of shunt conductance, GD = 2.5 mS/cm 2 and GL = 7.9 mS/cm 2 and series resistance, RD = 0.81 Ωcm 2 and RL = 0.19 Ωcm 2 were calculated for dark and illuminated conditions. Mott-Schottky analysis is also carried out on the final solar cell in dark and illuminated condition to study the carrier concentration and defects in the CdS/CIS interface.

Impact of rapid thermal (RT) annealing and normal selenization process on the properties of CuInSe 2 (CIS) layers prepared by electrochemical route is reported. Cyclic voltammetric measurement was carried out to optimize the co-deposition potentials. A range of characterization techniques were employed to study the properties. Three prominent reflections(112),(204/220) and (312/116) of tetragonal CIS were exhibited in as-deposited CIS layers. Upon selenization, the crystallinity was found to be improved. Uniform, compact, densely packed surface morphology was observed in as-prepared sample. Large grains are developed upon RT annealing due to recrystallization. Elemental composition obtained by EDAX confirms the growth of stoichiometric layers. Photo-electrochemical study demonstrates the p-type conductivity. Current-voltage, capacitance-voltage, electrochemical impedance spectroscopy were conducted to investigate the influence of the grain size and crystallinity on electrical properties. Energy band-gap estimated from absorption spectra were 1.18, 1.04 and 0.98 eV for as-deposited, selenized, RT annealed samples, respectively. X-ray Photoelectron spectroscopy confirms the presence of Cu + , In 3+ and Se 2− oxidation states in all CIS layers. Power conversion efficiency of 3.05% and 5.94% were achieved for selenized and RT annealed samples, respectively. The improved efficiency measured for RT annealed sample is proposed due to the growth of highly crystalline, large grain and compact surface morphology. Considering the energy crisis, solar energyhasemerged as an important non-conventional energy source. Various direct bandgap, high optical absorption coefficient materials have been used toward the fabrication of thin film solar cells. CuInSe 2 (CIS) is one of the intensively studied active absorber materials in solar cells because of its direct bandgap ∼1.05 eV, high absorption coefficient, large mean free pathand long diffusion length of minority carriers.1,2 Furthermore, the energy gap can be increased upon addition of gallium and/or sulfurization in controlled ambient. Device efficiency over 22% has been achieved for CIGS based thin film solar cells using co-evaporation method.3 However, in spite of high efficiency the high production cost is one of thesevere obstacles. Various reports are available in the literature on the development of CIS solar cells using vacuum 4 and non-vacuum processes.5 Electrochemical technique has been used for the preparation of CIS based solar cells.6 A low-cost electrochemical technique is widely used for the growth of metal oxide, insulator and semiconductor thin films because of higher growth rate, deposition over arbitrary shaped surface, possibility to grow highly crystalline and controlled stoichiometric alloy thin films. The best reported CIGS solar cells produced via this technique have measured 15.4% efficiency by Bhattacharya et al. 7 in conjunction with PVD method. Electrodeposition of CIS thin films can be performed either by one-step 8 or two-step approach. 9 Fabri...

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