| Since their advent in 2004,two-dimensional(2D)materials represented by graphene are the signifcant focus of researchers owing to their unique physical and chemical properties accompanied by complex mechanisms.An emerging family of 2D materials—transition metal chalcogenides(TMDCs)—exhibit high light absorption,high carrier mobility,and,in particular,the tunable bandgaps that cover a broad spectral range from UV-visible to infrared region can be tuned by composition and dimensionality,which offers great opportunities to develop many optoelectronic device applications,such as energy conversion,information communications and imaging.Moreover,because TMDCs can be conveniently prepared by various methods such as chemical vapor deposition(CVD),they are currently applied in many areas,such as photoelectric conversion and chemical production.However,the photoelectric performance of an individual 2D material is limited to its bandgap.To improve the photoelectric properties of the individual 2D material devices,the researchers proposed to construct multi-component 2D material heterojunctions which were expected to show outstanding advantages over individual 2D material by combining the excellent properties of each component.Of particular interest is to bypass difficulties in heteroepitaxy of lattice-mismatched constituent semiconductors of desired functionalities,which makes the 2D material heterojunctions have shown outstanding advantages over traditional semiconductor heterojunctions.In addition to the studies on the 2D/3D and 2D/2D heterojunctions,the researchers have focused on the 1D/2D,0D/2D and other heterojunctions including nanotubes,nanowires and quantum dots.The broad range of various materials with different properties and dimensionalities provides a wide platform for development of diverse nanophotonic devices by the combination of various properties.Perovskite materials have also received great attention because of their excellent photoelectric properties.The 2D/2D and 2D/3D heterojunctions between perovskites and 2D materials have been reported extensively,but the 0D/2D heterojunctions are rarely reported so far.Moreover,there is no an appropriate theoretical description on the complex energy band structure and the carrier behavior between the interfaces of the 0D/2D van der Waals(vd W)heterojunctions,which seriously hinders the further development of the 0D/2D vd W heterojunctions.In this paper,the high-quality Cs Pb Br3 perovskite quantum dots were prepared by using room temperature crystallization and hot injection methods,and the advantages and disadvantages of the two methods have also been systematically compared.Moreover,through doping treatment and surface ligand engineering,the stability and the range of fluorescence emission of Cs Pb Br3 perovskite quantum dots have been improved and expanded,respectively.Thus,a viable approach to effectively enhance the stability of perovskite quantum dots has been obtained.In addition,large-area preparation of singlelayer or few-layer high-quality Mo S2 films was explored,and the CVD preparation of large-area single-layer Mo S2 film has been finally realized under low-temperature and atmospheric pressure.Further,the 0D/2D type Cs Pb Br3/Mo S2 vd W heterojunctions have been successfully constructed by combining the prepared Cs Pb Br3 perovskite quantum dots and Mo S2 2D materials,significantly improving the performance of individual Mo S2 photovoltaic devices through a synergistic effect,which implies that the regulation of the photoelectric performance of 0D/2D vd W devices has been realized.The details are as follows:(1)The high-quality preparation,stability optimization and extension of the detection spectrum of Cs Pb Br3 perovskite quantum dots were systematically investigated.In this work,high-quality Cs Pb Br3 perovskite quantum dots were prepared by room temperature crystallization and thermal injection,and the advantages and disadvantages of the two methods were compared and studied.Further,through surface ligand engineering and rare earth Eu ion doping and so on,the stability and the detection spectrum range of Cs Pb Br3 perovskite quantum dots have been improved simultaneously,and thus the accompanying device performance has been enhanced.(2)The large-area growth of single-layer or few-layer high-quality 2D Mo S2 films was systematically studied.Through the introduction of a variety of activating elements during the CVD process,the thickness of the Mo S2 film prepared by the CVD method has been effectively controlled.The large-area CVD preparation of single-layer Mo S2 film has been finally realized under low-temperature and atmospheric pressure,which paves the way for the subsequent preparation and performance research of heterojunction devices.(3)The in-situ preparation and photoelectric performance of 0D/2D Cs Pb Br3/Mo S2 vd W heterojunction devices were deeply studied.In this work,by designing in-situ growth and spin coating methods to reduce the contamination caused by the general transfer method,0D/2D type Cs Pb Br3 quantum dots/Mo S2 vd W heterojunctions were successfully prepared in situ.The Cs Pb Br3/Mo S2 vd W heterojunction optoelectronic devices have been successfully fabricated and the optoelectronic performance of the individual Mo S2 devices has been significantly improved,for example,the responsivity(Ri)and specific detectivity(D*)have been improved by ?5 and ?4 orders of magnitude,respectively.Further,the photoresponse enhancement mechanism of the Cs Pb Br3/Mo S2 heterojunction devices was also studied.Excitingly,the extraordinary optoelectronic properties in the ranging of UV-Visible(405-655 nm)based on the Cs Pb Br3/Mo S2 heterojunction devices have been obtained,including Ri up to ?104-105 A/W,photoconductive gain(G)of ?108-1010 and D* of ?1011-1012 cm Hz1/2 W-1.In summary,this work provides a viable approach for the fabrication of low cost,low difficulty,and low pollution of the 0D/2D heterojunction photodetectors.Further,it provides a feasible route toward performance enhancement of perovskite quantum dot/2D material optoelectronic devices,which underpins strategies for controlling the interlayer coupling effect of 0D/2D vd W heterojunctions. |
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