Browsing by Author "Hu, Jyun-Yu"

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Field-Induced Fluorescence Quenching and Enhancement of Porphyrin Sensitizers on TiO2 Films and in PMMA Films
(2013-11-28)
Hsu, Hung-Yu
;
Chiang, Hung-Chu
;
Hu, Jyun-Yu
;
Awasthi, Kamlesh
;
Mai, Chi-Lun
Three highly efficient porphyrin sensitizers-YD2, YD2-oC8, and YD30, either sensitized on TiO2 films or embedded in PMMA films were investigated using electrophotoluminescence (E-PL) spectra. Under both thin-film conditions, on application of an external electric field we observed the quenching of fluorescence of push-pull porphyrins (YD2 and YD2-oC8) and a slightly enhanced fluorescence of the reference porphyrin without an electron donor group (YD30). A nonfluorescent state with charge separation (CS) is proposed to be involved in both YD2 and YD2-oC8 systems so that the electron injection becomes accelerated in the presence of a strong electric field. In contrast, the retardation of the nonradiative process not involving a CS state was the reason for the field-induced enhancement of fluorescence of YD30. The extent of fluorescence quenching of YD2-oC8 was greater than that of YD2 on TiO2 films, indicating that the ortho-substituted long alkoxyl chains play a key role to accelerate the consecutive electron injection involving the CS state. Our E-PL results indicate that a field-induced variation of fluorescent intensity is related to the efficiency of conversion of solar energy and that further improvement of the performance of devices containing push pull porphyrin dyes is achievable under an applied electric field.
Formation of size-tunable dandelion-like hierarchical rutile titania nanospheres for dye-sensitized solar cells
(2013)
Lan, Chi-Ming
;
Liu, Shang-En
;
Shiu, Jia-Wei
;
Hu, Jyun-Yu
;
Lin, Meng-Hung
A sol-gel method with a modified solvent comprising of three simple steps under low-temperature conditions was used to synthesize mono-disperse rutile TiO2 nanospheres with dandelion-like hierarchical morphology (DHRS) as a light-scattering layer for dye-sensitized solar cells (DSSC). 1,2-Ethanediol (ED) served as a key retardation agent in the second step at 25 degrees C to slow the hydrolysis and condensation of the TiCl4 aqueous solution prepared in the first step at 0 degrees C; the subsequent nucleation of a rutile type phase occurred homogeneously in the third step at 70 degrees C to generate the rutile TiO2 nanospheres with highly uniform sizes. The spherical sizes of DHRS were well controlled with the volume ratios of the ED-water solvent mixture in the second step, for which the DHRS of diameter 650-200 nm were produced from the solvent system containing 5-25% ED. A detailed mechanism is presented to rationalize the formation of nanospheres of uniform size in six steps: 1) hydration and hydrolysis, 2) hydrolysis and retardation, 3) hydrolysis and condensation, 4) homogeneous nucleation, 5) aggregation and growth of rod-like crystals and 6) DHRS formation. The DSSC device with a scattering layer made of DHRS (size similar to 300 nm) performed comparably to that with a scattering layer made of a commercially available TiO2 paste, making this nano-material a cost-effective alternative for future DSSC commercialization.
Highly efficient porphyrin-sensitized solar cells with enhanced light harvesting ability beyond 800 nm and efficiency exceeding 10%
(2014-04-01)
Wang, Chin-Li
;
Hu, Jyun-Yu
;
Wu, Cheng-Hua
;
Kuo, Hshin-Hui
;
Chang, Yu-Cheng
A new porphyrin sensitizer, LD31, was designed based on a donorp- pi-acceptor structure, in which an ethynyl-anthracenyl moiety was inserted between the dioctylaminophenyl group and the porphyrin core in order to extend the p-conjugation of the dye for improved light-harvesting ability. The device made of LD31 exhibited panchromatic spectral features covering the whole visible region and further extending over 800 nm. When combined with an organic dye (AN-4), the performance of the LD31/AN-4 co-sensitized device attained JSC/ mA cm(-2) = 20.3, VOC/mV = 704, FF = 0.72, and the overall efficiency of power conversion eta=10.3%.
Hybrid Titania Photoanodes with a Nanostructured Multi-Layer Configuration for Highly Efficient Dye-Sensitized Solar Cells
(2013-05-02)
Wu, Hui-Ping
;
Lan, Chi-Ming
;
Hu, Jyun-Yu
;
Huang, Wei-Kai
;
Shiu, Jia-Wei
To construct a hybrid titania photoanode containing nanoparticles and nanorods of varied size in a multilayer (ML) configuration for dye-sensitized solar cells, the essence of our ML design is a bilayer system with additional layers of nanorods of well-controlled size inserted between the transparent and the scattering layers to enhance the light harvesting capability for photosensitizers with small absorptivity, such as Z907. We measured charge-extraction and intensity-modulated photoelectric spectra to show the advantages of one-dimensional nanorods with an improved electron-transport property and an upward shift of the potential band edge; a favorable ML configuration was constructed to have a cascade potential feature for feasible electron transport from long nanorods, to normal nanorods, to small nanoparticles. On the basis of the ML system reported herein, we demonstrate how the performance of a Z907 device is improved to attain eta similar to 10%, which is a milestone for its future commercialization.
Novel expanded porphyrin sensitized solar cells using boryl oxasmaragdyrin as the sensitizer
(2013)
Mane, Sandeep B.
;
Hu, Jyun-Yu
;
Chang, Yu-Cheng
;
Luo, Liyang
;
Diau, Eric Wei-Guang
Oxasmaragdyrin boron complexes were prepared and applied in DSSCs. The HOMO-LUMO energy gap analyses and theoretical calculations revealed that these expanded porphyrins are ideal sensitizers for DSSCs. A device containing oxasmaragdyrin-BF2 as the sensitizer achieves an energy conversion efficiency of 5.7%.