N. Al-Hosiny

Tuning photocurrent response through size control of CdSe quantum dots sensitized solar cells

The photovoltaic characterization of CdSe quantum dots sensitized solar cells (QDSSCs) by tuning band gap of CdSe quantum dots (QDs) through size control has been investigated. Fluorine doped tin oxide (FTO) substrates were coated with 20 nm in diameter TiO2 nanoparticles (NPs). Pre-synthesized colloidal CdSe quantum dots of different sizes (from 4.0 to 5.4 nm) were deposited on the TiO2-coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electrolyte containing I−/I3− redox species was sandwiched between the two electrodes. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured for different dipping times, and AM 1.5 simulated sunlight. The maximum values of short circuit current density (Jsc) and conversion efficiency (η) are 1.62 mA/cm2 and 0.29 % respectively, corresponding to CdSe QDs of size 4.52 nm (542 nm absorption edge) and of 6 h dipping time. The variation of the CdSe QDs size mainly tunes the alignment of the conduction band minimum of CdSe with respect to that of TiO2 surface. Furthermore, the Jsc increases linearly with increasing intensity of the sun light, which indicates the sensitivity of the assembled cells.

Photoacoustic study of CdS QDs for application in quantum-dot-sensitized solar cells

The optical properties and photovoltaic characterization of CdS quantum dots sensitized solar cells (QDSSCs) were studied. CdS QDs were prepared by the chemical solution deposition (CD) technique. Photoacoustic spectroscopy (PA) was employed to study the optical properties of the prepared samples. The sizes of the CdS QDs were estimated from transmission electron microscope (TEM) micrographs gives radii ranged from 1.57 to 1.92 nm. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured. Fluorine doped Tin Oxide (FTO) substrates were coated with 20 nm-diameter TiO2 nanoparticles (NPs). Presynthesized colloidal CdS quantum dots of different particles size were deposited on the TiO2- coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electroelectrolyte containing I-/I3- redox species was sandwiched between the two electrodes. The short current density (Jsc) and efficiency (η) increases as the particle size increases. The values of Jsc increases linearly with increasing the intensities of the sun light which indicates the greater sensitivity of the assembled cells.

Characterization of carbon nanotubes (CNTs) polymethyl methacrylate (PMMA) composite films

Carbon nanotubes are considered as novel materials which have ultimate applications [1]. These nanotubes have been dispersed in many materials for exploring its new interesting properties. Polymethyl methacrylate (PMMA) is one of the most studied polymers due to its stability, low-cost, low optical loss in the visible spectrum, high scratch hardness and low glass temperature [2]. In this study, the optical and thermal properties of CNTs PMMA composite films were investigated. These composite films were prepared using casting method by dissolving PMMA in acetone with the ratio 1∶ 27 by which clear films were obtained. Several films PMMA + x wt% CNTs, where x = 0, 0.001 and 0.01, were prepared by dispersing CNTs in the polymeracetone solution ultrasonically for 30 min. The produced mixture was filtered and casted in petri dishes and left in air for three days. The obtained films were reasonably homogeneous and clear. The melting point of different films were determined using SCIENCO STA-1500 differential scanning calorimeter which was equipped with simultaneous thermogravimeter. The used temperature range was from room temperature to 420 °C with a heating rate of 5 °C/min. The films absorbance was determined by a spectrophotometer in the wavelength range from 450 nm to 4000 nm.

Carrier density dynamics in semiconductor lasers subject to dual optical injection

The dynamics of carrier density in semiconductor lasers subject to dual and single optical injection are compared, with special emphasis on the secondary locking region that lies outside the conventional locking bandwidth.