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Chang H.,National Taiwan University | Yang Y.-J.,National Taiwan University | Li H.-C.,National Taiwan University | Hsu C.-C.,National Taiwan University | And 2 more authors.
Journal of Power Sources | Year: 2013

We investigate the nanoporous TiO2 films sintered by atmospheric pressure plasma jets (APPJs) and their applications as photoanodes of dye-sensitized solar cells (DSSCs). A 30-s APPJ-sintered nanoporous TiO 2 layer exhibits an additional absorption band between 400 and 500 nm in wavelength, attributed to incomplete removal of the organic solvents in the pastes. For TiO2 layers sintered by APPJs for 60 s and beyond, the absorption spectra are nearly identical to those of a conventional 15 min, 510 °C calcined sample. The XRD and XPS results indicate similar characteristics for APPJ-sintered and furnace-sintered TiO2 films. A DSSC with a 30-s APPJ-sintered TiO2 photoanode shows poor cell efficiency with an extremely large TiO2/dye/electrolyte electron transport interfacial resistance and a short carrier lifetime. As the APPJ treatment time reaches 60 s and beyond, the power conversion efficiencies become comparable to that of a sample with a 510 °C conventionally calcined TiO2 photoanode. Our experimental results verify that a 60-s APPJ sintering process is sufficient to replace a conventional 15 min, 510 °C furnace calcination process for TiO2 photoanodes of DSSCs. The ultra-short sintering process is made possible by the synergistic effect of the temperature and the reactivity of the APPJ, which can lower the fabrication cost. © 2013 Elsevier B.V. All rights reserved. Source

Ho Y.-H.,Academia Sinica, Taiwan | Ho Y.-H.,National Taiwan University | Chen K.-Y.,Graduate Institute of Photonics and Optoelectronics | Peng K.-Y.,Academia Sinica, Taiwan | And 6 more authors.
Optics Express | Year: 2013

A precisely controlled metallic nanomesh was fabricated by using nanosphere lithography to pattern the silver thin film to form hexagonal nanohole arrays with excellent uniformity, high conductivity and good transparency. An Alq3 based OLED, with the silver nanomesh electrode of high fill factor of 70.2% demonstrated a considerable luminous efficiency of 4.8 cd/A, which is 60.9% higher than the referenced device with ITO anode. The periodical nanohole array not only increased the transparency but also helped extracting surface plasmonic wave in organic layers. By attaching the microlens array to further extract the trapped light in substrate, the extraction efficiency enhancement of device with nanomesh anode was 73.8% higher than 50.2% of the referenced device with ITO anode. And the overall current efficiency of device with nanomesh anode was 87.7% higher than traditional ITO based device. © 2013 Optical Society of America. Source

Mao M.-H.,No. 1 | Mao M.-H.,Graduate Institute of Photonics and Optoelectronics | Mao M.-H.,National Taiwan University | Chien H.-C.,No. 1 | And 5 more authors.
Optics Express | Year: 2011

We fabricated current-injection InGaAs quantum-dot microdisk lasers with benzocyclobutene cladding in this work. The microdisk pedestal diameter is carefully designed to facilitate carrier injection and modal control. With this structure, low threshold current of 0.45 mA is achieved at room temperature from a device of 6.5 μm in diameter with single-mode emission from quantum-dot ground states. The negative characteristic temperature T0 of threshold current is observed between 80 K and 150 K. The transition temperature from negative T0 to positive T0 is 150 K which is higher than that of the edge-emitting lasers fabricated from the same wafer. This phenomenon indicates the lower loss level of our microdisk cavities. These microdisk lasers also show positive T0 significantly higher than that of the edge-emitting lasers from the same wafer. © 2011 Optical Society of America. Source

Chou C.-T.,National Taiwan University of Science and Technology | Lin C.-H.,Graduate Institute of Photonics and Optoelectronics | Tai Y.,National Taiwan University of Science and Technology | Liu C.-H.J.,National Taiwan University of Science and Technology | And 3 more authors.
Journal of Physical Chemistry Letters | Year: 2012

In this Letter, we investigated the effect of the molecular stacking orientation on the open circuit voltage (V OC) of pentacene-based organic solar cells. Two functionalized pentacenes, namely, 6,13-diphenyl- pentacene (DP-penta) and 6,13-dibiphenyl-4-yl-pentacene (DB-penta), were utilized. Different molecular stacking orientations of the pentacene derivatives from the pristine pentacene were identified by angle-dependent near-edge X-ray absorption fine structure measurements. It is concluded that pentacene molecules stand up on the substrate surface, while both functionalized pentacenes lie down. A significant increase of the V OC from 0.28 to 0.83 V can be achieved upon the utilization of functionalized pentacene, owing to the modulation of molecular stacking orientation, which induced a vacuum-level shift. © 2012 American Chemical Society. Source

Liu S.-W.,Academia Sinica, Taiwan | Lee C.-C.,National Taiwan University of Science and Technology | Lin C.-F.,Graduate Institute of Photonics and Optoelectronics | Huang J.-C.,National Taiwan University of Science and Technology | And 2 more authors.
Journal of Materials Chemistry | Year: 2010

A stable exciton-blocking layer (EBL) with rigid ball-like 4-hydroxy-8-methyl-1,5-naphthyridine aluminium chelate (AlmND3) has been newly developed for organic photovoltaics (OPVs) based on a double-heterostructure of pentacene/C60/EBL. Unlike the common EBL materials, such as tris-(8-hydroxyquinoline)aluminium (Alq3) and bathocuproine (BCP), AlmND3 exhibits a relatively high electron mobility (∼10-4 cm2 V-1 s-1 at the electric field of 6.4 × 105 V cm-1) and a wide band gap energy (∼3.3 eV) in addition to a high glass transition temperature (Tg ∼ 194 °C). Having such EBL between active region (pentacene/C60) and the metal cathode, pristine device performances were comparable with those of BCP-based OPV due to its high mobility and wide band gap energy. Moreover, due to its significantly higher Tg than that of BCP, an extended lifetime performance was observed for AlmND 3-based OPV, compared with the BCP-based OPV aged at the elevated temperature of 75 °C. © 2010 The Royal Society of Chemistry. Source

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