He Tian,Xiancheng Meng,Juehan Yang,Chao Fan,Shuo Yuan,Xia An,Chun Sun,Yonghui Zhang,Mengjun Wang,Hongxing Zheng,Zhongming Wei,Erping Li
Two-dimensional (2D) nanomaterials have been attracting intensive interest due to their unique physical and optoelectronic properties. Van der Waals nanolayered heterostructures based on different 2D nanomaterials provide a state-of-the-art platform for investigating the physical phenomena and have extended the applications of 2D nanomaterials, leading to an era of next-generation high-performance electronic and optoelectronic technology. Herein, vertical 2D SnS/SnS2 p–n and SnSe2/SnS2 n–n nanolayered heterostructures are constructed by exfoliating individual materials and stacking them artificially. The two types of back-gate field-effect phototransistors show clear rectifying behaviors with the existence of band offset and excellent optoelectronic performances. The SnS/SnS2 p–n nanolayered heterostructure shows an ambipolar behavior with a hole mobility of 6.96 cm2·V–1·s–1 and electron mobility of 0.68 cm2·V–1·s–1, while the SnSe2/SnS2 n–n nanolayered heterostructure shows an intense n-type behavior with electron mobility of 3.78 cm2·V–1·s–1 and a high on/off ratio of over 105. Interestingly, due to the band alignments and built-in potentials in the two types of nanolayered heterostructures, the phototransistors exhibit enhanced responsive performances to illuminations of three-primary-color lasers (λ = 405, 532, and 650 nm) compared to the individual components. The SnS/SnS2 phototransistor shows a high photoresponsivity of 3567 A W–1, a high detectivity of 3.64 × 1013 Jones, and a fast response time of 0.8 ms. The SnSe2/SnS2 phototransistor also exhibits a high photoresponsivity of 1793 A W–1 and a fast response time of 15.4 ms.
Two-dimensional transition metal dichalcogenides (TMDs) have garnered significant attention in optoelectronic due to their unique structural and electronic properties. Among them, SnSe 2 and SnS 2 offer advantages of abundant reserves, low price and facile processing. In this work, we successfully synthesized SnSe 2 -SnS 2 nanosheets with an interesting lateral heterostructure via van der Waals edge epitaxial growth using a hydrothermal method. Density Functional Theory (DFT) calculations of surface energy and interfacial adhesion work revealed that the stronger covalent bonding between their (100) planes is the key thermodynamic factor governing the preferred lateral growth mode, despite their comparable lattice mismatch. The synergistic effect between the lateral heterojunction and the S-scheme interface with Se/S vacancies establishes a robust built-in electric field, which drastically promotes the excitation, separation, and migration of photogenerated charges, thereby significantly enhancing the photocatalytic activity. Evaluation of the photocatalytic performance demonstrated that the heterostructure degrades methyl orange (MO) at a rate 7.9 and 3.8 times faster than pure SnSe 2 and SnS 2 , respectively, and maintains over 70% of its initial activity after six consecutive cycles. This work provides mechanistic insights into the lateral growth mode of 2D materials and, through the synergistic design of band alignment and interface engineering, offers a novel paradigm for developing highly efficient and stable photocatalysts.
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