Here, Tetrabromophenol blue and Bromoxylenol blue with multibranched structures are chosen as sensitizers to study the optical and electrical properties for DSSCs, which structures and mutihydroxyl are hoped to enhance the charge transfer and adsorptivity.
Tetrabromophenol blue and Bromoxylenol blue with a purity of greater than 98.0% was obtained from Aladdin (Shanghai).
Ground-state structures and electronic structures of Tetrabromophenol blue and Bromoxylenol blue are optimized with DFT  using PBEPBE functionals [40-43] with 6-31G (d) basis set.
The chemical structures of the two dyes (Tetrabromophenol blue and Bromoxylenol blue) are shown in Figure 1.
In addition, the optical properties of Tetrabromophenol blue and Bromoxylenol blue are computed via TD-DFT/ PBEPBE/6-311G(d, p) in gas and solvent and the absorption spectra of two dyes are displayed in Figures 2(b) and 2(c).
Tetrabromophenol blue has three parts, which are sulfonic acid, 1,2,3,4-tetrabromobenzene, and 2,6-dibromophenol.
The electrochemical characteristics of Tetrabromophenol blue and Bromoxylenol blue are measured by cyclic voltammetry measurements in ethanol solvent, and the supporting electrolyte is KN[O.sub.3] , and the results are listed in Figures 4(a) and 4(b), showing that the onset oxidation potentials are 0.41 eV and -0.32 eV for Tetrabromophenol blue and 0.55 eV and -0.38 eV for Bromoxylenol blue, and they are obtained by the intersection of two tangent lines for the rising current curve and the starting current curve.
Recently, investigators have examined the influence of gamma irradiation on the color change of tetrabromophenol blue, the color change is influenced by the addition of chloral hydrate.
Preparation of stock solution of tetrabromophenol blue
The stock solution of the sodium salt of the indicator was prepared by dissolving 0.08 gm of tetrabromophenol blue indicator (TBPB).
Beshir, Radiation Sensitive Indicator Based on Tetrabromophenol Blue Dyed Poly (vinyl alcohol).