Quantitative Estimation of the Efficiency of Electron Injection from Excited Sensitizer Dye into Nanocrystalline ZnO Film

Abstract

The absolute value of the efficiency of electron injection from an excited coumarin dye (NKX-2311) into a nanocrystalline ZnO film was estimated as 0.8 ± 0.1 through transient absorption measurements. This value was obtained by using the molar absorption coefficient of the oxidized form of NKX-2311 determined in solution. Using this value and the previously obtained relative injection efficiency, we estimated the molar absorption coefficients of the oxidized form of N3 dye (cis-bis(4,4‘-dicarboxy-2,2‘-bipyridine)dithiocyanato ruthenium(II); Ru(dcbpy)2(NCS)2) and the conducting electrons in the ZnO film.

Effect of excitation wavelength on electron injection efficiency in dye-sensitized nanocrystalline TiO2 and ZrO2 films

“…These results clearly show that the electron injection is very fast and the recombination is slow, which is consistent with previous observations [7]. We already estimated the absorption coefficient of the oxidized form (N3 + ) of N3 dye as 6000 mol −1 dm 3 cm −1 [6]; therefore the efficiency of electron injection can be estimated quantitatively from the observed absorbance change. Fig.…”

“…The absorbance changes are proportional to the excitation light intensity. Under this condition, the efficiency of electron injection U inj can be written in terms of the absorbance change due to the generation of N3 + (DA ox ) and the molar absorption coefficient e ox of N3 + [6]:…”

“…We [3][4][5][6][7][8][9] and others [10][11][12][13][14][15][16][17][18][19][20][21][22] have extensively used transient absorption spectroscopy to study electron injection processes. The dynamics of electron injection has been studied by femtosecond laser spectroscopy, and electron injection has been found to complete within 10 ps [15][16][17][18][19][20].…”

“…Recently, we quantitatively estimated the efficiency for N3 dye (cis-bis(4,4′-dicarboxy-2,2′-bipyridine)di(thiocyanato)ruthenium(II); Ru(dcbpy) 2 (NCS) 2 ) adsorbed on a nanocrystalline TiO 2 film (abbreviated N3/TiO 2 ); the estimated efficiency was 95% under 532-nm excitation [6]. The efficiency of electron injection is sensitive to experimental conditions, such as excitation light intensity [7] and concentration of Li + [11,12].…”

Ultrafast Charge‐Transfer Reactions of Indoline Dyes with Anchoring Alkyl Chains of Varying Length in Mesoporous ZnO Solar Cells

“…[9] Electron injection from the excited dye to the semiconductor is an important part of device optimization. Electron injection from various dyes into ZnO has been studied [11][12][13][14][15] and it has been clarified that the injection from the excited dye to Dye-sensitized solar cells based on a mesoporous ZnO substrate were sensitized with the indoline derivatives DN91, DN216 and DN285. The chromophore is the same for each of these dyes.…”