Umme Farva

Elucidation of morphological and optoelectronic properties of highly crystalline chalcopyrite (CuInSe2) nanoparticles synthesized via hot injection route

CuInSe2 (CIS) nanoparticles have been prepared by the hot-injection method with sizes ∼25 nm, and the thermal annealing influence on the size, morphology and optoelectronic properties of crystalline CuInSe2 nanoparticles has been elucidated. Microstructural analysis of synthesized nanoparticles was performed by various characterization methods including high-resolution transmission electron microscopy (HR-TEM), Scanning TEM (STEM), Xray diffraction, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The fast Fourier transform (FFT) pattern of HR-TEM image of annealed CuInSe2 nanoparticles illustrates that the particles have quasisingle crystal tetragonal structure, as also confirmed by the XRD pattern. The HR-TEM image clearly shows the fringe widths are in order without any defect with 0.32 nm. Microstructural analysis results clearly indicate that the synthesized and air-annealed nanoparticles are in highly crystalline state with near stoichiometric atomic composition.

Optimization study of copper precursors for high quality CuInSe 2 nanoparticles by wet chemical route

High-quality CuInSe2 nanoparticles have been prepared by the solution phase synthesis procedure utilizing copper acetate or cuprous chloride as the Cu-precursor, indium chloride as the In-precursor and selenium powder as Se precursor, respectively. The synthesis process was optimized to grow 20 to 150 nm sized nanostructures of CuInSe2, and the Cu to In ratio as well as the kind of Cu-precursor used was found to be most important in determining the structure and property of the nanostructures. The synthesized nanostructures were characterized by TEM (transmission electron microscopy), XRD (X-ray diffraction), PL (photoluminescence) and micro-Raman spectroscopy, and detailed microstructural analyses of synthesized samples were also carried out by selective area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM).

Optoelectronic properties of CdSe nanoparticles and their application to bulk hetero-junction solar cells

The CdSe nanoparticles have been synthesized by hot-injection method, and thermal annealing was used to improve the crystallinity of synthesized nanoparticles and reconstruct the surface of nanoparticles. The synthesized and annealed CdSe nanoparticles were characterized by TEM, XRD and PL spectra. After thermal annealing followed by a solvent exchange process, the CdSe nanoparticles were used to fabricate bulk hetero-junction solar cells of CdSe/P3HT active layer. The morphology control of nanoparticle-polymer composite films was also investigated. By varying only the concentration of the binary solvent mixture, the phase separation behavior between the nanoparticles and blended polymer could well be controlled from micrometer scale to nanometer scale, yielding uniform and reproducible active layer films.

Effect of post annealing on the performance of CdSe/P3HT bulk hetero-junction solar cells

Thermal annealing effect on the structural and optical properties of synthesized CdSe nanoparticles has been elucidated and applied on the performance improvement of bulk hetero-junction solar cell. Improvement in crystallinity and cell stabilization of as-synthesized CdSe nanoparticles could be achieved by controlling the annealing parameters. Synthesized and annealed CdSe nanoparticles were characterized by TEM, XRD, XPS, Raman and PL measurements. XRD analysis exhibited annealing-induced phase transition in the nanocrystalline CdSe from cubic Zinc Blende to hexagonal Wurtzite structure. After annealing, the intensity of PL emission peak was substantially increased, and the solar cell with optimized active layer showed enhancement in power conversion efficiency. Post-annealing process parameters for solar cell fabrication were developed based on the studies of thermal annealing effect on CdSe nanoparticles.

Surface morphological and electrical characterization of thin film CdSe/P 3 HT composite layer for bulk hetero-junction solar cells

A blend of cadmium selenide quantum dots with conjugated polymer poly (3-hexylthiophene-2,5-diyl) (P3HT) was investigated as an active layer for the bulk hetero- junction solar cell. The surface morphology of composite active layer was controlled and investigated in relation to the bulk hetero-junction solar cell performance. Use of a binary solvent was intensively studied to improve the surface morphology. Smooth and uniform active layer surface could be obtained at optimum binary solvent composition with controlled drying process. The active layer sheet resistance was measured by using the transmission line method (TLM), and it was found that the percolation pathway for charge carrier transport could be developed above the threshold CdSe loading concentration