Photogenerated Charge Harvesting and Recombination in Photocathodes of Solvent-Exfoliated WSe2
Photogenerated Charge Harvesting and Recombination in Photocathodes of Solvent-Exfoliated WSe2
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DOI：
10.1021/acs.chemmater.7b02018
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发表时间：
2017-08
影响因子：
8.6
通讯作者：
Xiaoyun Yu;K. Sivula
中科院分区：
文献类型：
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作者：
Xiaoyun Yu;K. Sivula
了解和优化超薄过渡金属二卤化物(TMD)半导体光电极的边态和纳米片尺寸对光子捕获效率的影响，对于评估其在太阳能转换方面的实用可行性至关重要。我们提出了一种新的基于过滤的分离方法来系统地改变溶液处理的大面积多片WSe2光电阴极的TMD纳米片尺寸和边缘密度。在水电解液(用于水还原)和牺牲氧化还原体系中的光电化学测量，结合基于连续介质的电荷传输模型，揭示了边缘位置的作用和片层尺寸对光捕获、电荷传输和复合的影响。开发了一种使用原子层沉积的选择性钝化技术，以解决片状边缘的有害复合问题。用最小的片层(∼150 nm宽，9 nm厚)制备的边缘钝化的WSe_2薄膜显示出明显的内耗.
Understanding and optimizing the effects of edge states and nanoflake dimensions on the photon harvesting efficiency in ultrathin transition-metal dichalcogenide (TMD) semiconductor photoelectrodes is critical to assessing their practical viability for solar energy conversion. We present herein a novel filtration-based separation approach to systematically vary the TMD nanoflake dimensions and edge density of solution-processed large-area multiflake WSe2 photocathodes. Photoelectrochemical measurements in both aqueous electrolyte (for water reduction) and a sacrificial redox system, together with a continuum-based charge transport model, reveal the role of the edge sites and the effects of the flake size on the light harvesting, charge transport, and recombination. A selective passivation technique using atomic layer deposition is developed to address detrimental recombination at flake edges. Edge-passivated WSe2 films prepared with the smallest flakes (∼150 nm width, 9 nm thickness) demonstrate an intern...