Shasha Zhou

Crystal organometal halide perovskites with promising optoelectronic applications

Organometal halide perovskites AMX3 (A = organic cation, M = metal cation, and X = halogen anion) have been dominating the photovoltaic fields with an unexpected sharp efficiency enhancement to 20.1% in the past five years. Furthermore, the extraordinary properties of optical absorption, photoluminescence and low non-radiative recombination rates extend their applications into optoelectronic fields beyond photovoltaic devices. This review briefly outlines the state-of-the-art research activities of crystal perovskite AMX3, describes the fundamental optoelectronic properties, specific morphologies and related synthesis techniques, and summarizes their functions in optoelectronic fields such as solar cells, lasers, light-emitting diodes and photodetectors. Finally, the general challenges and the potential future directions of this exciting research area are highlighted.

Tunneling Diode Based on WSe2/SnS2 Heterostructure Incorporating High Detectivity and Responsivity

van der Waals (vdW) heterostructures based on atomically thin 2D materials have led to a new era in next-generation optoelectronics due to their tailored energy band alignments and ultrathin morphological features, especially in photodetectors. However, these photodetectors often show an inevitable compromise between photodetectivity and photoresponsivity with one high and the other low. Herein, a highly sensitive WSe2 /SnS2 photodiode is constructed on BN thin film by exfoliating each material and manually stacking them. The WSe2 /SnS2 vdW heterostructure shows ultralow dark currents resulting from the depletion region at the junction and high direct tunneling current when illuminated, which is confirmed by the energy band structures and electrical characteristics fitted with direct tunneling. Thus, the distinctive WSe2 /SnS2 vdW heterostructure exhibits both ultrahigh photodetectivity of 1.29 × 1013 Jones (Iph /Idark ratio of ≈106 ) and photoresponsivity of 244 A W-1 at a reverse bias under the illumination of 550 nm light (3.77 mW cm-2 ).

Space-confined vapor deposition synthesis of two dimensional materials

Two dimensional (2D) nanomaterials are promising fundamental building blocks for use in the next-generation semiconductor industry due to their unique geometry and excellent (opto)-electronic properties. However, large scale high quality fabrication of 2D nanomaterials remains challenging. Thus, the development of controllable fabrication methods for 2D materials is essential for their future practical application. In this review, we will discuss the importance of the space-confined vapor deposition strategy in the controllable fabrication of 2D materials and summarize recent progress in the utilization of this strategy for the synthesis of novel materials or structures. Using this method, various high quality ultrathin 2D materials, including large-area graphene and boron nitride, ReS2/ReSe2, HfS2, pyramid-structured multilayer MoS2, and the topological insulators Bi2Se3 and Bi2Te3, have been successfully obtained. Additionally, by utilizing van der Waals epitaxy growth substrates such as mica or other 2D materials, patterned growth of 2D nanomaterials can be easily achieved via a surface-induced growth mechanism. Finally, we provide a short prospect for future development of this strategy.

Temperature Difference Triggering Controlled Growth of All-Inorganic Perovskite Nanowire Arrays in Air

All-inorganic perovskites have attracted increasing worldwide interest due to its significantly improved stability in atmospheric environment compared to organic-inorganic hybrid perovskites, which renders it infinitely applicable in many fields such as electronics, optoelectronics, and energy storage. However, all-inorganic perovskites have to confront the challenges from fabrication before their wide utilization in the aforementioned applications. Liquid-phase synthesis holds the advantage of mass production and easy modulation of composition but with the deficiencies of relatively low crystallinity and disordered products. Interestingly, gas-phase growth has complementary characteristics compared to the liquid-phase method. In this work, it is proposed that a novel temperature difference triggers growth strategy to integrate the merits of the liquid- and gas-phase methods, and the feasibility of this strategy via a simple lab-use hot plate is demonstrated. High quality all-inorganic perovskites, cesium lead halide (CsPbX3 ) nanowire arrays, can be epitaxially grown as in a gas-phase method, but at the same time, the composition of products can be easily modulated by predesigning the recipe of precursors as in the liquid-phase method on a large scale. Notably, the as-fabricated CsPbX3 perovskite nanowire arrays demonstrate excellent stability and good optoelectronic properties in air. It is believed that this novel strategy can strikingly prompt the development of perovskites fabrication and applications in future.

Temperature dependence of Raman responses of few-layer PtS2

Platinum disulfide (PtS2) is a newly emerging 2D material, which possesses relatively high carrier mobility, a widely tunable band gap from 0.25 to 1.6 eV, and ultra-high air stability, showing a potential in electronics and optoelectronics. Here, for the first time, we study the temperature-dependent Raman spectra on PtS2 with different thicknesses. It was found that with the temperature increase from 80 to 298 K, the [Formula: see text] and [Formula: see text] modes of all samples show linear softening. Moreover, the linear softening with temperature of PtS2 is much smaller than other 2D transition metal dichalcogenides, which could be attributed to the stronger interlayer coupling in PtS2. Our work gives fundamental temperature-dependent vibrational information of PtS2, which will be useful in future PtS2-based electronic devices.