Browsing by Author "Bhattacharya, Dibyendu"

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Enhanced light-harvesting capability by phenothiazine in ruthenium sensitizers with superior photovoltaic performance
(2012)
Yin, Jen-Fu
;
Chen, Jian-Ging
;
Lin, Jiann-T'suen
;
Bhattacharya, Dibyendu
;
Hsu, Ying-Chan
This paper reports on the design and synthesis of two new ruthenium dyes [Ru(dcbpy)(potip)(NCS)(2)] (JF-3, dcbpy 4,4'-dicarboxylic acid-2,2'-bipyridine, potip 2-(4-(10H-phenothiazin-10-yl)-5-octylthiophen- 2-yl)-1H-imidazo[4,5-f][1,10] phenanthroline, and [Ru(dcbpy)(dpotip)(NCS)(2)] (JF-4, dpotip = 2-(4-(N,N-diphenylamino)-5-octylthiophen-2-yl)-1H-imidazo[4,5-f][1,10] phenanthroline) that contain electron-donating phenothiazine-based or N,N-diphenylamino-based ancillary ligands. The ruthenium dye JF-3, in which an excellent electron-donating phenothiazine is incorporated, shows superior DSC performance (9.1%; compared to 8.8% for N3). A comparison of the electron-donating phenothiazine and N, N-diphenylamino groups utilized in the molecular architecture of ruthenium dyes demonstrates that the phenothiazine group efficiently increases the molar extinction coefficient of band II and also broadens that band in the UV-vis absorption spectrum, reduces device resistance, increases electron lifetime, and enhances power-conversion efficiency. This finding not only clarifies the significance of multifunctionalized design in the molecular architecture of ruthenium dyes, but also represents an alternative route for the introduction of an excellent electron-donating group for improving the light-harvesting characteristics of ruthenium dyes as well as DSC performance.
Enhanced photovoltaic performance by synergism of light-cultivation and electronic localization for highly efficient dye-sensitized solar cells
(2009)
Yin, Jen-Fu
;
Bhattacharya, Dibyendu
;
Hsu, Ying-Chan
;
Tsai, Chen-Chuan
;
Lu, Kuang-Lieh
Two ruthenium sensitizers, [Ru(dcbpy)(opip)(NCS)(2)] (JF-1, dcbpy 4,4'-dicarboxylic acid-2,2'-bipyridine, opip = 2-(4-octylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ru(dcbpy)(otip)(NCS)(2)] (JF-2, otip = 2-(5-octylthiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), with unusually high power-conversion efficiency in comparison with other ruthenium complexes containing 1,10-phenanthroline-based ligands were designed. The power-conversion efficiency of JF-2 is 20% higher than that of JF-1, due to the modification of the ancillary ligand with a thiophene moiety. The origins of this device performance diversity are illustrated by photophysical properties, electrochemical data and density functional theory (DFT) studies. The greater device performance of JF-2 compared to JF-1 was caused from the broader MLCT distribution, the appropriate localization of the frontier orbitals and the stronger driving force of the charge injection and regeneration.
Structural planarity and conjugation effects of novel symmetrical acceptor-donor-acceptor organic sensitizers on dye-sensitized solar cells
(2012-04-01)
Chu, Hsuan-Chih
;
Sahu, Duryodhan
;
Hsu, Ying-Chan
;
Padhy, Harihara
;
Patra, Dhananjaya
In this study two series of novel symmetrical acceptor-donor-acceptor organic sensitizers containing 3,6- and 2,7-functionalized carbazole cores, respectively, connected to two anchoring cyanoacrylic acid termini via thienyl linkers were synthesized. The effect of the molecular planarity originating from the 3,6- and 2,7-functionalized carbazole cores on the performance of corresponding solar cells were investigated. Molecular orbital analyses revealed the characteristics of the carbazole-based highest occupied molecular orbitals and acid-based lowest unoccupied molecular orbitals. Time-dependent density functional theory calculations allowed us to assign the electronic transitions (>90%) of the low energy bands. Among these new dyes, the highest power conversion efficiency of 4.82% was obtained in a dye-sensitized solar cell device under standard AM 1.5 sunlight with an open-circuit voltage of 0.61 V, a short-circuit photocurrent density of 12.66 mA cm(-2) and a fill factor of 0.62. (C) 2011 Elsevier Ltd. All rights reserved.
Structure optimization of ruthenium photosensitizers for efficient dye-sensitized solar cells - A goal toward a "bright" future
(2012-12-01)
Yin, Jen-Fu
;
Velayudham, Murugesan
;
Bhattacharya, Dibyendu
;
Lin, Hong-Cheu
;
Lu, Kuang-Lieh
Research on dye-sensitized solar cells (DSC) is progressing at a rapid pace. The structural and electronic factors associated with ruthenium photosensitizers can have a significant effect on the performance of DSCs. This review emphasizes the recent developments and strategies employed in the structural design of ruthenium photosensitizers. The influence of molecular engineering on photophysical and electrochemical properties along with photovoltaic parameters and the efficiency of DSCs are also reviewed. Hence, drawing a correlation between the structure of photosensitizers, the properties and photovoltaic parameters of corresponding DSCs will be helpful in terms of optimizing new dyes for the generation of efficient solar cells. (c) 2012 Elsevier B.V. All rights reserved.