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EED-Newsletter-Vol-2-Issue-1-2017

PAGE 22

PAGE 22 EED PhD Graduate Students Thesis Title: Organic/Inorganic Semiconductor Based Opto-electronic Devices: Light Detectors and Dye-Sensitized Solar Cells. Ali Sehpar Shikoh Mr. Ali Sehpar Shikoh received his B.S. degree in Electrical Engineering from University of Engineering and Technology (UET), Lahore, Pakistan. In 2011, he got enrolled in for an MSc degree in Renewable Energy Systems & Technology offered by Loughborough University, UK. During the tenure of his enrollment at Loughborough University, he got involved in various extracurricular activities alongside serving as the elected “Postgraduate Representative” for the Electrical Engineering Department. After his graduation, he worked as a fixed-term R.A. at Loughborough University and later joined Qatar University in 2013. During his tenure at Qatar University he worked as a research assistant on an NPRP project related to fabrication and characterization of high performance transparent conducting electrodes (TCEs) for solar cell applications. At present, he is enrolled in as a PhD student in the electrical engineering department of Qatar University and is planning to present his defense in December, 2017. In addition, he also had frequent opportunities to present his research work at various reputed research forums, both in and outside of Qatar. To this date, he has six journal publications to his name alongside numerous conference publications. Emerging opto-electronic devices (e.g. light sensors and solar cells) based on thin-film devices have been greatly emphasized, owing to their many interesting properties including low cost, reduced weight, high flexibility and solution processability. The underlined thesis was aimed to enhance the performance of optoelectronic devices by means of optimizing processes associated with their fabrication and investigating different device configurations. In the first phase, improvements in the electrical and photodetection properties of thin film devices were done. The opto-electronic devices based on a dye sensitized semiconductor layer showed a larger leakage current (i.e. 1.35 µA) when sensitized with one of the most predominantly used (Ruthenium based) N719 sensitizing dye. In a bid to reduce the leakage current and improve the rectification behaviour of the fabricated devices, co-sensitization of N719 with AS-2 dye was carried out. This led to a significant reduction in the leakage current (to around 0.18 µA)alongside increased linearity and higher breakdown voltage. Nevertheless, properties like sensitivity and responsivity resided within acceptable ranges. Also, promising photodetection results were also achieved when the TiO 2 active layer was completely replaced with PCBM:P3HT, thereby creating a hybrid device DSSC/ BHJ configuration, Figure 1. In the second phase, a new type of CuNWs, rGO and PEDOT:PSS based counterelectrode was developed to replace ITO/Pt counterelectrode, present in the dyesensitized photosensor (DSPS) assembly, shown in Figure 2. The fabricated hybrid electrode exhibited high transparency(> 90%) and low sheet resistance (20 Ω cm -2 ). Upon Figure 1 integration in DSPS device, the CuN- Ws/rGO/PEDOT:PSS based counter-electrode displayed long-term stability and produced superior performance in terms of photodetection parameters such as response time, reset time and responsivity. Lastly, focus was paid on optimizing the photovoltaic properties of the TiO 2 photoelectrodes by means of altering semiconductor layer deposition and post-deposition (sintering) processes. A novel technique known as electrophoretic deposition (EPD) was utilized for the preparation of photo-anodes. During this process, various deposition EPD voltage levels ranging from 2.5 V to7.5 V were uti- Figure 2 EED NEWSLETTER VOL. 2, ISSUE 1

VOLUME 1, ISSUE 1 PAGE 23 lized. When integrated within DSSCs, the photo-anode containing TiO 2 semiconductor layer deposited at 5 V DC produced the highest efficiency of 4.2%. A further increase of 6.66% in efficiency was achieved due to the restring nucleation and growth (i.e. altered crystallinity) of anatase nanoparticles, when post-deposition single step sintering was replace with two-step sintering process, Figure 3. These results are expected to have a profound effect on solar cell and photo-detection industry by fostering improvement of thin-film optoelectronic devices. Figure 3 EED NEWSLETTER VOL. 2, ISSUE 1

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