Papers by Keyword: Photosensitivity

Abstract: Ultraviolet photodetectors (PDs) based on low-dimensional (LD) gallium oxide nanofibers were synthesized and assembled by a low cost and scalable electrospinning method. Highly uniaxially aligned nanofibers were used to assemble photodetectors. Photoconductive investigations indicate that the prepared photodetectors (PDs) are highly sensitive to ultraviolet (UV) light. The prepared photodetectors have shown a high photosensitivity (10³), fast photoresponse, excellent stability, and reproducibility under the illumination of UV light 254 nm. These electrospun nanofibers have also shown a high transparency (<85%) in the visible light 400-700 nm range. The high transparency of these nanobelts demonstrates their use for invisible UV photosensors.

Abstract: CdS_xTe_1-x (0 ≤ x ≤ 1) thin films were prepared on clear quartz glass substrate by close spaced sublimation method using stoichiometric mixed powders of pure CdS and CdTe compounds. Crystal structure of CdS_xTe_1-x thin films was cubic structure with a preferential orientation of (111) plane when the S mole ratio less than 0.2. However, For the composition 0.2 ≤ x ≤ 0.8, the cubic and the hexagonal phases were found to coexist in the system and the films became less preferentially oriented whereas CdS thin films formed in the hexagonal phase with a preferential orientation of (002) plane. SEM micrographs showed the grain size decreased when the S content increased. As the S content increased, the energy gap value of CdS_xTe_1-x thin films varied from 1.48 eV (for CdTe) to 2.25 eV (for CdS). Dark electrical sheet resistance of CdS_xTe_1-x thin films decreased as a function of S content to minimum value about 2.24×10⁷ Ω/sq for x=0.8 and then slightly increased to 4.13×10⁷ Ω/sq for x=1.0. From the transient photoconductivity measurements, the highest photosensitivity value about 60.0 was obtained for the films with x = 0.8.

Abstract: Coherent pre-illumination technique is proposed to improve the pulsed holographic recording characteristics of polyvinyl alcohol (PVA) /acrylamide green-sensitive photopolymer. By optimizing the pre-illumination parameters such as pre-illumination energy density and pre-illumination delay time, the photosensitivity and diffraction efficiency of photopolymer under pulsed holographic recording are improved effectively. For the coherent pre-illumination energy density of 2mJ/cm², total pre-illumination energy of 50mJ/cm², the diffraction efficiency of 85% can be obtained with holographic exposure of 35mJ/cm². For the coherent pre-illumination delay time of 20seconds, the diffraction efficiency of 60% is obtained with holographic exposure of 17.5mJ/cm². The photosensitivity is successfully improved about 8 times compared with other reported results, it has good application prospects in the measurements of high-speed transient processes.

Abstract: The organic photoelectric transistors using the vacuum evaporation and sputtering process are prepared in this paper. The Cu/CuPc/Al/CuPc/ITO layer based on vertical structure is grown through a CuPc active layer. The CuPc has excellent photosensitivity and it is easy to be fabricated into Short-Channel device with vertical structure. It is shown that I-V characteristics of organic photoelectric transistors are unsaturated. In this experiment the light source is the Bromine-tungsten lamp in the range of 300nm to 800nm. When the light source irradiates the device with V_ec=2V, the operating current is 0.155μA which has been increased to 2.3-3.6 times as compared with the dark state. Therefore, the amplification coefficient of output current I_ec is increasing in irradiation with smaller base voltage. As a result, the current amplification coefficient β is 5.25 and 2.14 with illumination and without illumination respectively.

Abstract: Multi-component doped photopolymer with phenanthrenequinone photosensitizers is prepared and its photosensivity characteristic is investigated experimentally. SiO₂ nanoparticles and ZnMA organometallic components are dispersed into the P(MMA-co-MAA) matrix to enhance the photosensitivity of sample. Experimental results indicate the photopolymerization time constants under consecutive exposure and the time constants of dark enhancement under darkness are evidently reduced at least one order of magnitude.

Abstract: Hydrogenated amorphous silicon germanium thin films (a-SiGe:H) were prepared via plasma enhanced chemical vapor deposition (PECVD). By adjusting the flow rate of GeH4, a-SiGe:H thin films with narrow bandgap (Eg) were fabricated with high Ge incorporation. It was found that although narrow Eg was obtained, high Ge incorporation resulted in a great reduction of the thin film photosensitivity. This degradation was attributed to the increase of polysilane-(SiH2)n, which indicated a loose and disordered microstructure, in the films by systematically investigating the optical, optoelectronic and microstructure properties of the prepared a-SiGe:H thin films via transmission, photo/dark conductivity, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) measurements. Such investigation provided a helpful guide for further preparing narrow Eg a-SiGe:H materials with good optoelectronic properties.