Two Dimensional Materials/Silicon Nanopillar Arrays Heterojunction Photoelectric Devices

Two-dimensional materials have been a hot spot in recent years because of its unique electronic properties.The graphene is a typical two-dimensional material and can be used as electrode materials for flexible solar cells due to its transparent,conductive and flexible properties.In addition,the topological insulator(TI)is also a two-dimensional material.Its unique metallic Dirac surface states and narrow bulk band gap can extend the absorption spectrum to infrared band,so it is an important material of infrared photoelectric detector.The excellent properties of two-dimensional materials in optics and electricity make them have great potential in the application of photoelectric devices.However,the research of two-dimensional materials is just starting at present,and more innovative application is yet to be studied.As a member of silicon nanostructure family,silicon nanopillar arrays(SiNPs)not only have the comparable light absorption capability but also with the large effective contact area in heterojunction compared to silicon nanowires(SiNWs).What's more,we can effectively control the height and size of the SiNPs via process parameter setup to achieve the balance between the incident light absorption and the device contact area so as to gain the ideal device efficiency.In this dissertation,a large area of SiNPs is prepared based on the technology of polystyrene spheres mask and reactive ion etching.The obtained SiNPs were combined with graphene and topological insulators to build high performance solar cells and photodetectors,respectively.The main contents of this dissertation are as follows;1.The Si nanowires(SiNWs)are the common Si nanostructures,and the drawback of the heterojunction of SiNWs and two-dimensional materials is the small contact area.SiNPs have not only the comparable light absorption capability but also with the large effective contact area in heterojunction compared to silicon nanowires(SiNWs).We present the SiNPs by using the polystyrene(PS)nanospheres as a mask and combining reactive ion etching(RIE)technology,and adjust the etching forming gas ratio and etching time to optimize the light absorption of SiNPs.2.The performance of the two-dimensional materials and SiNWs heterojunction devices was restricted by the small contact area in the heterojunction.We used SiNPs instead of the SiNWs which was synthesized by the wet teching technology to fabricate the solar cells based on graphene/SiNPs heterojunction.The graphene/SiNPs heterojunction had the comparable light absorption performance comparing to graphene/SiNWs heterojunction,in addition,it also enlarged the contact area between graphene and SiNWs which improved the performance of the device.Finally,10.15%efficiency of the device was achieved.3.The narrow bulk band gap of topological insulator can only form a small barrier to prevent carrier recombination which makes poor photodetection performance.However,the heterojunction combined by topological insulators and the SiNPs can form a strong schottky barrier at the interface,the built-in potential can effectively promote the photon-generated carrier separation and transport.We fabricated the Bi2Se3/SiNPs heterojunction photodetector by generating the Bi2Se3 film on the surface of SiNPs via chemical vapor deposition(CVD)technology.The SiNPs was used to instead of the planar Si to enhance the light absportion of the device,finally the responsivity of 6.26 AW'1 was achieved.In addition,the detect spectrum range of Bi2Se3/SiNPs heterojunction photodetectors can be extended to optical communication(1550 nm).4.As a new subset of topological insulator materials(TIs),topological crystal insulator(TCIs)has the unique properties such as high symmetry of the crystal structures,multiple surface states,and tunable electronic properties.The high quality and large area TCI SnTe films were prepared by chemical vapor deposition(CVD),and the SnTe/SiNPs heterojunction photodetector was fabricated by combining of SnTe and SiNPs.The performance of the device has been improved comprehensively by the introduction of narrow band gap TCIs material and SiNPs,finally the responsivity of 8.8 AW-1,the detectivity of 8.8 x1012 cmHz1/2w-1,the response speed of 8.8 ?s were achieved.In addition,the detect spectrum range of SnTe/SiNPs heterojunction photodetectors can cover from ultraviolet to near-infrared.