Applied Physics Program, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, USA.
J Am Chem Soc. 2012 Jun 27;134(25):10670-81. doi: 10.1021/ja304019n. Epub 2012 Jun 18.
The steady-state photoelectrochemical responses of p-GaP photoelectrodes immersed in aqueous electrolytes and sensitized separately by six triphenylmethane dyes (rose bengal, rhodamine B, crystal violet, ethyl violet, fast green fcf, and brilliant green) have been analyzed. Impedance measurements indicated that these p-GaP(100) photoelectrodes operated under depletion conditions with an electric field of ∼8.5 × 10(5) V cm(-1) at the p-GaP/solution interface. The set of collected wavelength-dependent quantum yield responses were consistent with sensitization occurring specifically from adsorbed triphenylmethane dyes. At high concentrations of dissolved dye, the measured steady-state photocurrent-potential responses collected at sub-bandgap wavelengths suggested unexpectedly high (>0.1) net internal quantum yields for sensitized hole injection. Separate measurements performed with rose bengal adsorbed on p-GaP surfaces pretreated with (NH(4))(2)S verified efficient sensitized hole injection. A modified version of wxAMPS, a finite-difference software package, was utilized to assess key operational features of the sensitized p-GaP photocathodes. The net analysis showed that the high internal quantum yield values inferred from the experimental data were most likely afforded by the internal electric field present within p-GaP, effectively sweeping injected holes away from the interface and minimizing their participation in deleterious pathways that could limit the net collection yield. These simulations defined effective threshold values for the charge carrier mobilities (≥10(-6) cm(2) V(-1) s(-1) and ≥10(-1) cm(2) V(-1) s(-1) at dopant densities of 10(18) and 10(13) cm(-3), respectively), hole injection rate constants (≥10(12) s(-1)), and surface trap densities (10(12) cm(-2)) needed to attain efficient hole collection with the quality of p-GaP materials used here. The cumulative experimental and modeling data thus provide insight on design strategies for assembling new types of dye-sensitized photocathodes that operate under depletion conditions.
已分析了浸入水溶液电解质中的 p-GaP 光电管在分别被六种三苯甲烷染料（玫瑰红、罗丹明 B、结晶紫、乙基紫、快绿 fcf 和亮绿）敏化后的稳态光电化学响应。阻抗测量表明，这些 p-GaP(100)光电管在耗尽条件下工作，在 p-GaP/溶液界面处的电场约为 8.5×10(5) V cm(-1)。收集的一组依赖波长的量子产率响应与特定从吸附的三苯甲烷染料发生的敏化一致。在溶解染料的高浓度下，在亚带隙波长下收集的稳态光电流-电位响应表明，敏化空穴注入的净内部量子产率出乎意料地高（>0.1）。用（NH(4))(2)S 预处理的 p-GaP 表面上吸附的玫瑰红进行的单独测量证实了敏化空穴注入的有效。有限差分软件包 wxAMPS 的修改版本用于评估敏化 p-GaP 光电阴极的关键操作特性。净分析表明，从实验数据推断出的高内部量子产率值很可能是由 p-GaP 内存在的内部电场提供的，有效地将注入的空穴从界面上扫出，并最小化它们参与可能限制净收集产率的有害途径的参与。这些模拟定义了电荷载流子迁移率（在掺杂密度分别为 10(18) 和 10(13) cm(-3)时，≥10(-6) cm(2) V(-1) s(-1)和≥10(-1) cm(2) V(-1) s(-1)）、空穴注入速率常数（≥10(12) s(-1)）和表面陷阱密度（10(12) cm(-2))的有效阈值值，以实现这里使用的 p-GaP 材料的高效空穴收集。因此，累积的实验和建模数据提供了关于组装在耗尽条件下运行的新型染料敏化光电阴极的设计策略的见解。
