Size-dependent photocurrent switching in chemical bath deposited CdSe quantum dot films
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- 作者：М. V. Malashchonak ; E. A. Streltsov…
- 关键词：CdSe ; Quantum dots ; Chemical bath deposition ; Photocurrent switching ; Underpotential deposition
- 刊名：Journal of Solid State Electrochemistry
- 出版年：2017
- 出版时间：March 2017
- 年：2017
- 卷：21
- 期：3
- 页码：905-913
- 全文大小：
- 刊物类别：Chemistry and Materials Science
- 刊物主题：Physical Chemistry; Electrochemistry; Energy Storage; Characterization and Evaluation of Materials; Analytical Chemistry; Condensed Matter Physics;
- 出版者：Springer Berlin Heidelberg
- ISSN：1433-0768
- 卷排序：21
文摘
Size-dependent photocurrent switching has been investigated in chemical bath deposited CdSe quantum dot (QD) films with band gaps 2.26, 2.09, and 1.81 eV (corresponds to nanoparticles’ average diameter of 4, 5, and 10 nm). CdSe films generate only anodic photocurrent (exhibit n-type semiconductor behavior) in the solution which contains only acceptor of photoholes (SO32− anions), whereas cathodic photocurrent (corresponding to p-type behavior) arises after immersion of the films in polyselenide electrolyte (containing Sen2−/Se2− redox system). Appearance of the cathodic photocurrent is related to chemisorptions of Se2− and Sen2− anions, as revealed by the cadmium underpotential deposition (UPD). Photocurrent switching from anodic to cathodic becomes more pronounced with decreasing of CdSe nanoparticle size because small quantum dots with their broadened band gaps have more favorable conduction band energy for electron injection to polyselenide anions. On the contrary, particle size does not play a significant role for the injection of photoholes into the electrolyte because the position of the valence band is weakly size-dependent, and anodic photocurrent is determined primarily by the real surface area of the electrode, which was found to be greater than the geometrical one by 1–2 orders of magnitude from cadmium UPD. Effective charge separation at the highly developed CdSe-electrolyte interface contributes to high incident photon-to-current conversion efficiency of photocurrent (IPCE ~40 %).