الفهرس 
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Abstract
In this work, photodetectors for near-infrared (NIR) lasers with organic semiconductor material as active layer were experimentally investigated. The structural and optical properties of two different organic semiconductor materials were studied.Thin films of titanyl phthalocyanine (TiOPc) and fullerene (C60) were deposited using conventional thermal evaporation technique. The prepared films were studied before and after thermal annealing. The crystal structure was studied using X-ray diffraction (XRD) technique and the chemical structure was studied using Fourier transform infrared (FTIR) spectroscopy technique. The surface morphology was studied using field emission scanning electron microscope (FESEM). The optical properties were studied using spectrophotometric measurements in the spectral range 200-2500 nm. The optical constants (refractive index, n, and absorption index, k) were determined as well as the values of the optical band gap.The XRD showed that the TiOPc films structure transformed from amorphous to crystalline α-phase when thermally annealed at 160 ºC for 4 h. The FESEM images showed a clear increase in particle size by annealing. The values of the indirect band gap were found to be 1.48 eV and 2.5 eV for the as deposited film and shifted to 1.15 eV and 2.19 eV for the annealed film. The XRD of C60 films showed that its structure was transformed from the stable face-centered-cubic (fcc) structure to the unstable hexagonal close-packed (hcp) structure when thermally annealed at 250 ºC for 10 h. The FESEM images showed that the films are of nanostructure. The values of direct band gap were found to be 2.33 eV, 3.14 eV, and 3.35 eV for the as deposited film and were found to be 2.59 eV and 3.23 eV for the annealed film.Photodetctors with the layer structure of (Ag/TiOPc/p-Si/Al) and (Al/C60/TiOPc/n-Si/Au) were fabricated using conventional thermal evaporation technique. The current-voltage (I-V) characteristics of the fabricated photodetectors were measured in dark and under illumination of white light and near-infrared laser. The responsivity, the external quantum efficiency (EQE), and the detectivity of the fabricated photodetectors were determined. Also, the response time of the two photodetectors was measured.The Ag/TiOPc/p-Si/Al photodetector exhibited rectification with ratio of 4.3 at bias of 2 V at room temperature. Under illumination of 805 nm NIR laser, the photodetector was found to have responsivity, EQE, and detectivity of 1.63x10-5 A/W, 0.0025%,and 1.22x107 Jones, respectively at a revese bias of -2 V. The photodetector was found to have a fall time of about 34 μs. The Al/C60/TiOPc/n-Si/Au photodetector exhibited rectification with ratio of 2.13 at bias of 2 V at room temperature. Under illumination of 805 nm NIR laser, the photodetector was found to have responsivity, EQE, and detectivity of 1.95x10-4 A/W, 0.03%, and 4x107 Jones, respectively at a reverse bias of -2 V. The photodetector was found to have a fall time of about 30 μs.