Browsing by Author "Chang, I-Jy"

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Alkyl-Spacer Enhancement in Performance of Light-Emitting Electrochemical Cells
(1970-01-01)
Shiu, Ler-Chun
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Chang, Bo-Ren
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Hsiao, Miles C-S
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Sie, Wu-Sian
;
Wu, Ming-Lun
Synthetic, structural, photophysical, and electrochemical study of [Ir(ppy)(2)(py)(2)](BF4) (1(BF4)) and four di-N-N-bridged complexes of [Ir(ppy)(2)(bpa)](2)(BF4)(2)(2A(BF4)(2)), [Ir(ppy)(2)((cis-bpe))](2)(BF4)(2)(2B(BF4)(2)), [Ir(ppy)(2)(tmp)](2)(BF4)(2)(2C(BF4)(2)), and [Ir(ppy)(2)(bpy)](4)(BF4)(4)(3(BF4)(4)) are described with Hppy = 2-phenylpyridine, py = pyridine, N-N= dipyridyl ligands of 1,2-bis(4-pyridyl)ethane (bpa),cis-1,2-bis(4-pyridyl)ethylene (cis-bpe), 1,3-di(4-pyridyl)propane (tmp), and 4,4'-dipyridine (bpy). Five single-crystal structures of1(PF6),2A(NO3)(2),2A(PF6)(2),2B(PF6)(2), and3(NO3)(4)were determined, supporting the dibridged structures and presence of a variety of stereoisomers. Application of four luminescent complexes,1(BF4),2A(BF4)(2),2C(BF4)(2), and3(BF4)(4), in solid-state light-emitting electrochemical cells (LECs) is reported. The work demonstrates an effective approach to realize efficient LECs based on dibridged di- and multinuclear cationic transition-metal complexes with a suitably long alkyl spacer in the bridging ligand.
Relaxation dynamics of ruthenium complexes in solution, PMMA and TiO2 films: The roles of self-quenching and interfacial electron transfer
(2007-09-06)
Chang, Chih-Wei
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Chou, Chung Kuang
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Chang, I-Jy
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Lee, Yuan-Pern
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Diau, Eric Wei-Guang
The relaxation dynamics of two transition-metal complexes, [Ru(bpy)(3)](2+) and [Ru(bpy)(3)(mcbpy)](2+), in ethanol solution and in poly(methyl methacrylate) (PMMA) and TiO2 films have been investigated with time-resolved emission and femtosecond transient absorption spectroscopy. The emission lifetime of a degassed [Ru(bpy)3]21 solution in ethanol was determined to be 700 ns; to describe the self-quenching kinetics due to aggregation, three decay coefficients, 5.3, 70, and 220 ns, were obtained for the [Ru(bPY)(3)](2+)/PMMA film. The electron transfer through space in a [Ru(bpy)(3)](2+)/TiO2 film competed with intrinsic intersystem crossing (similar to 100 fs) and vibrational relaxation (similar to 6 ps) in solid films. For the [Ru(bpy)(2)(mcbpy)](2+)/TiO2 film, although the relaxation for electron transfer through bonds was more rapid than electron transfer through space, both processes occur on similar time scales. Through ferntosecond transient absorption measurements, we provide important dynamical evidence for the interfacial electron transfer in both forward and backward directions. We conclude that in dye-sensitized solar-cell applications processes for interfacial electron transfer are significant not only through bonds but also through space.