揭示空间电荷区域以外的光载流子动力学，用于光电化学水分解,Chemistry of Materials

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揭示空间电荷区域以外的光载流子动力学，用于光电化学水分解
Chemistry of Materials ( IF 7.2 ) Pub Date : 2017-04-18 00:00:00 , DOI: 10.1021/acs.chemmater.7b00672
Wenrui Zhang ₁ , Danhua Yan _{1,

2} , Kannatassen Appavoo ₁ , Jiajie Cen ₂ , Qiyuan Wu ₂ , Alexander Orlov ₂ , Matthew Y. Sfeir ₁ , Mingzhao Liu ₁

Affiliation

用于光电化学（PEC）分解的半导体光电极需要在水界面处形成的空间电荷区（SCR）处以及其外进行有效的载流子生成，分离和传输。光子收集与少数载流子输送之间的权衡决定了光电极的设计，并暗示了在等于光吸收深度的电极厚度下最大的水分解效率。在这里，使用平面ZnO薄膜作为模型系统，我们将SCR以外的光载流子确定为实质上提高PEC性能的另一个重要来源。通过脉冲激光沉积合成的高质量ZnO薄膜具有极低的深陷阱态，并具有较长的光载流子寿命。结合光电化学表征，超快光谱和数值计算，揭示了通过膜厚度对激子浓度梯度进行工程设计有助于光载流子从相邻照明区域向SCR的向内扩散，因此在远远超过其光吸收深度和厚度的厚度下实现了创纪录的80％以上的量子效率。 SCR宽度。这些结果阐明了除SCR以外的光载流子在PEC过程中的重要作用，并为探索具有大激子扩散率的有效光电极材料的全部潜力提供了新的见识。在远远超过其光吸收深度和SCR宽度的厚度下，实现了超过80％的创纪录的高量子效率。这些结果阐明了除SCR以外的光载流子在PEC过程中的重要作用，并为探索具有大激子扩散率的有效光电极材料的全部潜力提供了新的见识。在远远超过其光吸收深度和SCR宽度的厚度下，实现了超过80％的创纪录的高量子效率。这些结果阐明了除SCR以外的光载流子在PEC过程中的重要作用，并为探索具有大激子扩散率的有效光电极材料的全部潜力提供了新的见识。

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Unravelling Photocarrier Dynamics beyond the Space Charge Region for Photoelectrochemical Water Splitting

Semiconductor photoelectrodes for photoelectrochemical (PEC) water splitting require efficient carrier generation, separation, and transport at and beyond the space charge region (SCR) formed at the aqueous interface. The trade-off between photon collection and minority carrier delivery governs the photoelectrode design and implies maximum water splitting efficiency at an electrode thickness equivalent to the light absorption depth. Here, using planar ZnO thin films as a model system, we identify the photocarriers beyond the SCR as another significant source to substantially enhance the PEC performance. The high-quality ZnO films synthesized by pulsed laser deposition feature very few deep trap states and support a long photocarrier lifetime. Combined with photoelectrochemical characterization, ultrafast spectroscopy, and numerical calculations, it is revealed that engineering the exciton concentration gradient by film thickness facilitates the inward diffusion of photocarriers from the neighboring illuminated region to the SCR and, therefore, achieves a record high quantum efficiency over 80% at a thickness far beyond its light absorption depth and the SCR width. These results elucidate the important role of the photocarriers beyond SCR for the PEC process and provide new insight into exploring the full potential for efficient photoelectrode materials with large exciton diffusivity.

更新日期：2017-04-28

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