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KIST, South Korea

Mohammed M.,University of Arkansas at Little Rock | Mohammed M.,Solar Cell Research Center | Li Z.,University of Al-Qadisiyah | Li Z.,University of Michigan | Chen T.-P.,University of Arkansas at Little Rock
Journal of Renewable and Sustainable Energy | Year: 2016

A new type of n-p-n transistor photovoltaic device based on CdS/multi-wall carbon nanotube (MWNT)/n-Si configuration was fabricated in a facile process. CdS quantum dots were deposited on fluorine-doped tin-oxide glass using a chemical bath deposition method, and MWNT film was coated on n-type Si substrate by airbrushing. The materials used for the n-p-n transistor solar cells were characterized by multiple techniques including X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman, Ultraviolet visible (UV-vis) spectrophotometer, and I-V characteristic measurements. The CdS layer acts as a good n-type material for the transistor solar cells. The thickness of the CdS layer can be controlled by the chemical bath deposition time to achieve different photovoltaic responses. I-V characteristic measurements show that the efficiency increases with increasing the thickness of the CdS thin layer. Compared with the tandem solar cells based on (p/n)-(p/n) semiconductor junctions, our n-p-n transistor solar cell has a simple structure without using tunnel junctions or wafer bonding schemes for interconnecting the cells. © 2016 AIP Publishing LLC. Source

Kim S.,Dongjin Semichem. Co. | Lim H.,Inha University | Kim K.,Inha University | Kim C.,Inha University | And 4 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2010

Low-bandgap organic sensitizers are designed and synthesized for high photocurrent generation in dye-sensitized solar cell. Introduction of the π-conjugated benzothiadiazole (BTD) unit in K1, designated as K2, decreases the highest occupied molecular orbitallowest unoccupied molecular orbital (HOMOLUMO) gap energy from 2.63 to 2.10 eV, whereas the photovoltaic performance is not improved although the absorption threshold in incident photon-to-current conversion efficiency spectrum is extended from 650 nm to approximately 800 nm. Low photovoltaic performance is overcome by introduction of a phenylenevinylene moiety next to the BTD unit in K2, designated as K3 that shows similar HOMOLUMO gap energy and absorbance to those of K2. As a result, a K3-sensitized 5 μ m-thick TiO2 solar cell demonstrates photocurrent density of 12.24 mA/cm2, voltage of 0.549 V, and conversion efficiency of 3.8%, which is better than the conversion efficiency of 2.49% for K2 with photocurrent density of 8.13 mA/cm2and voltage of 0.470 V. According to nanosecond transient absorption spectroscopic study, photoexcited electron injection efficiency of K3 is found to be three times higher than that of K2, which is attributed to the higher photocurrent of K3. © 2006 IEEE. Source

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