Unsymmetrical Heptamethine Dyes for NIR Dye-Sensitized Solar Cells

Table 1

Optical properties of the unsymmetrical and symmetrical heptamethine dyes in ethanol.

Dye^a	𝜆max (nm)^b	𝜀(𝜆max) (Lcm^−1mol^−1)^c	𝑓^d	𝜆^absonset (nm)^e	𝐸^opt𝑔 (eV)^f
Hepta1	790	133000	1.8	882	1.41
Hepta2	795	100000	1.5	888	1.40
Hepta3	754	94600	1.7	866	1.43
Hepta4	758	82500	1.4	852	1.46
Hepta5	702	51700	0.9	896	1.38
Hepta6	788	108000	1.5	830	1.49
Hepta7	810	240000	1.3	847	1.46
symHepta1	850	262000	1.9	894	1.39
symHepta2	797	357000	2.0	830	1.49
symHepta3	799	227000	1.3	835	1.48

aChemical structures of the symmetrical heptamethine dyes are given in the Supplementary Material. ^bAbsorption maximum, UV-vis spectra of all dyes are represented in the Supplementary Material. ^cMolar absorption coefficient determined from the absorbance for a molar concentration (𝑐≈2×10⁻⁶ molL⁻¹) of the dyes with a path length of 1 cm at 𝜆_max. ^dOscillator strength, 𝑓=4.31×10⁻⁹ ∫𝜀(𝜐)𝑑𝜐. ^eOnset absorption edge at higher wavelengths. ^fOptical band gap, 𝐸^opt_𝑔 = hc/𝜆^abs_onset.