Abstract
Two-dimensional (2D) tungsten disulfide (WS2) has inspired great efforts in optoelectronics, such as in solar cells, light-emitting diodes, and photodetectors. However, chemical vapor deposition (CVD) grown 2D WS2 domains with the coexistence of a discontinuous single layer and multilayers are still not suitable for the fabrication of photodetectors on a large scale. An emerging field in the integration of organic materials with 2D materials offers the advantages of molecular diversity and flexibility to provide an exciting aspect on high-performance device applications. Herein, we fabricated a photodetector based on a 2D-WS2/organic semiconductor materials (mixture of the (Poly-(N,N′-bis-4-butylphenyl-N,N′-bisphenyl) benzidine and Phenyl-C61-butyric acid methyl ester (Poly-TPD/PCBM)) heterojunction. The application of Poly-TPD/PCBM organic blend film enhanced light absorption, electrically connected the isolated WS2 domains, and promoted the separation of electron-hole pairs. The generated exciton could sufficiently diffuse to the interface of the WS2 and the organic blend layers for efficient charge separation, where Poly-TPD was favorable for hole carrier transport and PCBM for electron transport to their respective electrodes. We show that the photodetector exhibited high responsivity, detectivity, and an on/off ratio of 0.1 A/W, 1.1 × 1011 Jones, and 100, respectively. In addition, the photodetector showed a broad spectral response from 500 nm to 750 nm, with a peak external quantum efficiency (EQE) of 8%. Our work offers a facile solution-coating process combined with a CVD technique to prepare an inorganic/organic heterojunction photodetector with high performance on silicon substrate.
Highlights
Two-dimensional materials (2D), such as graphene, hexagonal boron nitride, transition metal dichalcogenides, tin sulfide, black phosphorus, ultrasmall bismuth quantum dots, and selenium nanoflakes, have become optically active semiconductors in biomedicine, ion detectors, and photodetectors (PDs)
There was no ZnO X-ray diffraction (XRD) peak that existed after complete 2D WS2 growth (Figure 2a) [34], which was further confirmed by the X-ray photoelectron spectroscopy (XPS) spectrum, since no Zn2+ signal (Zn 2P1/2 at 1021.75 eV and Zn 2P3/2 at 1044.7 eV) was detected [49]
We attribute the excellent photoresponse to the appropriate band gap, the high quality of the chemical vapor deposition (CVD)-grown single/multilayer WS2, and the energy-favorable heterojunction
Summary
Two-dimensional materials (2D), such as graphene, hexagonal boron nitride, transition metal dichalcogenides, tin sulfide, black phosphorus, ultrasmall bismuth quantum dots, and selenium nanoflakes, have become optically active semiconductors in biomedicine, ion detectors, and photodetectors (PDs). Photodetector-based graphene exhibits a large-response wavelength range and a high on/off ratio. Photodetector-based monolayer transition metal dichalcogenides (TMDs) show high quantum efficiency and low response times [1,2,3,4,5,6,7,8,9,10,11,12]. Among these 2D materials, tungsten disulfide (WS2) layers with high mobility of 1000 cm2·v−1·s−1, a high optical absorption coefficient of ca. Among these 2D materials, tungsten disulfide (WS2) layers with high mobility of 1000 cm2·v−1·s−1, a high optical absorption coefficient of ca. 106 cm−1, and a band gap of 1.9 eV [13,14,15,16] are typical n-type 2D materials for electronic and optoelectronic device applications, making them compatible to combine with other materials to construct 2D van der Waals heterostructures
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