Department of Physics, City College of New York , New York, New York 10031, United States.
Department of Materials Science & Technology, National Tsing Hua University , Hsinchu City, Taiwan.
Nano Lett. 2017 May 10;17(5):3176-3181. doi: 10.1021/acs.nanolett.7b00695. Epub 2017 Apr 12.
We study the optoelectronic properties of a type-II heterojunction (HJ) comprising a monolayer of the transition metal dichalcogenide (TMDC), WS, and a thin film of the organic semiconductor, 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA). Both theoretical and experimental investigations of the HJ indicate that Frenkel states in the organic layer and two-dimensional Wannier-Mott states in the TMDC dissociate to form hybrid charge transfer excitons at the interface that subsequently dissociate into free charges that are collected at opposing electrodes. A photodiode employing the HJ achieves a peak external quantum efficiency of 1.8 ± 0.2% at a wavelength of 430 ± 10 nm, corresponding to an internal quantum efficiency (IQE) as high as 11 ± 1% in these ultrathin devices. The photoluminescence spectra of PTCDA and PTCDA/WS thin films show that excitons in the WS have a quenching rate that is approximately seven times higher than in PTCDA. This difference leads to strong wavelength dependence in IQE.
我们研究了由单层过渡金属二卤化物（TMDC）WS 和有机半导体 3,4,9,10-苝四羧酸二酐（PTCDA）薄膜组成的 II 型异质结（HJ）的光电性质。对 HJ 的理论和实验研究表明，有机层中的 Frenkel 态和 TMDC 中的二维 Wannier-Mott 态解离形成界面处的混合电荷转移激子，随后解离成自由电荷，在对向电极处收集。采用 HJ 的光电二极管在 430 ± 10nm 的波长处实现了 1.8 ± 0.2%的峰值外量子效率，对应于这些超薄器件中高达 11 ± 1%的内量子效率（IQE）。PTCDA 和 PTCDA/WS 薄膜的光致发光光谱表明，WS 中的激子猝灭速率大约比 PTCDA 高七倍。这种差异导致 IQE 具有强烈的波长依赖性。
