Construction Of Two-dimentional In₂Se₃ Based Heterojunctions And Its Photoelectric Performance

In recent years,two-dimensional materials have attracted wide attention in the field of nano-optoelectronic devices due to their unique physical and chemical characteristics such as high in-plane electron mobility and very sensitive band gap to surface states.Among them,indium selenide?In₂Se₃?,an important type of III-VI semiconductors with direct and narrow band gap,high sensitivity,and high absorption coefficient in the ultraviolet to visible and infrared ranges,has become one of the most promising materials for photovoltaic devices.Compared to graphene and transition metal sulfide,there is still less research on indium selenide by scientists,and many potential properties of In₂Se₃ await to be explored.In this paper,monomer In₂Se₃ samples with different morphologies and phases obtained by three preparation methods were used to construct a light-conducting photodetector,and the difference in photoelectric performance was studied.In₂Se₃/Zn O and In₂Se₃/Si heterojunctions were fabricated respectively.The photoelectric conversion capabilities and carrier transport mechanism of heterojunctions were explored.An In₂Se₃/Se/Si ternary composite system was established and its photodetection properties and difference from the binary heterojunctions was investigated.The main contents are as follows:1.2D In₂Se₃ with different morphologies and structures were prepared by hydrothermal method,solvothermal method and chemical vapor deposition method,respectively.Photoconductive photodetectors based on various monomers In₂Se₃ were constructed,and it was found that the 2D In₂Se₃ synthesized by different methods have photoresponse in the range of 300-800 nm,but the current switching ratio and time stability are different.Generally speaking,the dark and light current of the samples are in the n A level,the switch ratios are maintained between 10-100,and the response time stay within 3s.These results shows that although the single In₂Se₃ has a fast response speed,the low conductivity has limited its application.So it can be combined with other materials to build high-performance photoelectric device.2. Through the transfer method,the In₂Se₃/Zn O heterojunction was constructed by Zn O array and the 2D In₂Se₃ nanosheets.Combining the conductivity and the light absorption characteristics of the two materials,the heterojunction shows a photoresponse range from UV-NIR region.The response speed and stability of Zn O array were greatly improved,and the response time is decreased to 0.18s,which reduced tenfold than the traditional Zn O.The composite structure has the highest response to 480 nm light and its photoresponse curve,external quantum efficiency,and detectivity were calculated,indicating the decent detection characteristics.3. Dense 2D array of In₂Se₃ nanosheets was grown by chemical vapor deposition on a silicon substrate,and the AFM figures proved this structure.The obtained In₂Se₃/Si p-n junction detector shows excellent stability and fast response speed?0.15 ms/0.5 ms?.It is calculated that the photo responsivity?97 m A/W?,is highest under the light of 980 nm,which proves the significant near-infrared light response characteristics of the p-n junction.4. The ternary composite system In₂Se₃/Se/Si was grown in situ by chemical vapor deposition method,it was found that the composite structure showed lower darkness than the In₂Se₃/Si heterojunction.The higher photocurrent and switch ratio,excellent stability and fast response speed show that the ternary system has stronger photoelectric conversion ability.Under the light of 880 nm,the maximum optical responsivity,external quantum efficiency and detectivity are reaching 932 m A/W,34%,and 3×10¹⁴ jones,respectively.The internal electric field and synergy between different materials of the composite structure promote the generation and separation of electrons,making them exhibit better near-infrared photoelectric properties.