Sensitization of p-GaP with Monocationic Dyes: The Effect of Dye Excited-State Lifetime on Hole Injection Efficiencies

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• 作者：Stefan Ilic ; Elizabeth S. Brown ; Yun Xie ; Stephen Maldonado ; Ksenija D. Glusac
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 18, 2016
• 年：2016
• 卷：120
• 期：6
• 页码：3145-3155
• 全文大小：560K
• ISSN：1932-7455

文摘

The sensitized hole injection to the p-type gallium phosphide (p-GaP) electrode was evaluated for several triarylmethane (6Op>+p>), acridine (4Op>+p>, 2Op>+p>, Me₂N-Acrp>+p>, T-Acrp>+p>), and flavin dyes (Et-Flp>+p>). Thermodynamics for sensitized charge injection were evaluated using steady-state ultraviolet–visible absorption and cyclic voltammetry experiments. All dyes (except 4Op>+p>) had strong absorption at wavelengths above 550 nm (absorption cutoff for GaP), and their highest occupied molecular orbital energies were below the valence band of GaP (+1.20 V vs normal hydrogen electrode), indicating that the electron transfer from p-GaP electrode to the excited dye molecules was thermodynamically favorable. Photoelectrochemical measurement conducted on p-GaP electrodes immersed in aqueous electrolytes and dye showed sensitization for only two dyes (2Op>+p> and Et-Flp>+p>), and the sensitization efficiencies were found to depend on the chemical nature of differently prepared p-GaP electrodes. Femtosecond pump–probe measurements revealed that the “inefficient” dyes had short-lived excited states (few picoseconds), preventing the successful charge transfer into p-GaP surface. Collectively, this work provides insight on time scales of hole-injection rates during dye-sensitization processes.