Ye Lei, Zhao Yujie, Xu Rong, Li Shuangshuang, Zhang Chunfeng, Li Hanying, Zhu Haiming
Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China.
J Am Chem Soc. 2023 Dec 6;145(48):26257-26265. doi: 10.1021/jacs.3c09119. Epub 2023 Nov 23.
Sensitizing inorganic semiconductors using singlet fission (SF) materials, which produce two excitons from one absorbed photon, can potentially boost their light-to-electricity conversion efficiency. The SF sensitization is particularly exciting for two-dimensional (2D) layered semiconductors with atomically flat surface and high carrier mobility but limited light absorption. However, efficiently harnessing triplet excitons from SF by charge transfer at organic/inorganic interface has been challenging, and the intricate interplay among competing processes remains unresolved. Here, we investigate SF sensitization in high-quality organic/2D bilayer heterostructures featuring TIPS-Pc single crystals. Through transient magneto-optical spectroscopy, we demonstrate that despite an ultrafast SF process in sub-100 fs, a significant fraction of singlet excitons in TIPS-Pc dissociate at the interface before fission, while triplet excitons from SF undergo diffusion-limited charge transfer at the interface in ∼10 ps to ns. Remarkably, the photocharge generation efficiency reaches 126% in heterostructures with optimal thickness, resulting from the competitive interplay between singlet exciton fission, dissociation, and triplet exciton transport. This presents a promising strategy for advancing SF-enhanced 2D optoelectronics beyond the conventional limits.
使用单重态裂变（SF）材料敏化无机半导体，该材料可从一个吸收的光子产生两个激子，这有可能提高其光电转换效率。对于具有原子级平整表面和高载流子迁移率但光吸收有限的二维（2D）层状半导体而言，SF敏化尤其令人兴奋。然而，通过有机/无机界面处的电荷转移有效地利用来自SF的三重态激子一直具有挑战性，并且竞争过程之间复杂的相互作用仍未得到解决。在这里，我们研究了以TIPS-Pc单晶为特征的高质量有机/2D双层异质结构中的SF敏化。通过瞬态磁光光谱，我们证明尽管在亚100飞秒内存在超快SF过程，但TIPS-Pc中的很大一部分单重态激子在裂变前在界面处解离，而来自SF的三重态激子在界面处经历扩散限制的电荷转移，时间约为10皮秒至纳秒。值得注意的是，在具有最佳厚度的异质结构中，光电荷产生效率达到126%，这是由于单重态激子裂变、解离和三重态激子传输之间的竞争相互作用所致。这为超越传统限制推进SF增强的2D光电子学提供了一种有前景的策略。
