Research Of Photodetector With 0D-2D Hybrid Structure

Photodetectors have been widely applied in the fields of video system,optical communication,night vision and military reconnaissance in modern society.The development of technology requires the improvement of device performance.To accomplish this will,it need to synthesize the high performance photosensititive materials and develop device based on novel structure and mechanism.The new materials need to break through the limitation of silicon and can absorb the light in a broad waveband from UV to IR.It also should have a high gain for the device fabricated by the materials.In the past studies,nanomaterials with low dimensionality were regarded as the ideal detection materials because of their unique optoelectronic properties.This paper synthesized a series of nanomaterial with zero dimensionality?0D?and two dimensionality?2D?by optimizing the synthetic process.Based on these quantum dots?QDs?,nanocrystals?NCs?and nanosheet,we fabricated the novel photodetector with hybrid structure.The light sensitizing layer with high absorptivity can improve the light absorption efficiency of the photodeteor and the two dimensional materials with high mobility can transfer the photocarried efficiently.With the synergistic effect of them,high performance photodetector can be accomplished.The work content in this paper was summarized as follows:?1?PbS QDs with zero dimensionality were synthesized by hot injection method and two dimensional WSe₂ monolayer was grown by CVD method.We combined them together by spin coating method and faricated the PbS QDs/WSe₂ hybrid photodetector.The device shows a responsivity up to 2×10⁵ A/W,which is orders of magnitude higher than the counterpart of individual material based devices.The hybrid phototransistors obtain a specific detectivity of 7×10¹³ Jones and a low darkcurrent.PbS QDs can efficiently absorb the input infared illumination and trap the photoelectrons causing a photogating effect toward the 2D WSe₂ layer.And the high gain of hybrid 0D-2D phototransistor is ascribed to the synergistic function of photogating effect.The present device construction strategy with 0D-2D structure,photogating effect and type II band sturcture made it a high performance photodetector which is potential device for future optoelectronic devices.?2?A facile aqueous solution method was developed for the preparation of large-scale 2D lead dihalide nanosheets.By modulating the components of halogens,the bandgap of nanosheets could be tuned to meet varied detection spectra.High-performance UV photodetectors were successfully implemented based on them.For PbI₂ photodetectors,they were dominantly driven by a photoconduction mechanism and showed a fast response speed and a low noise current density.An I_ON/I_OFF ratio up to 10³,a response time of 700?s and a high normalized detectivity of 1.5×10¹² Jones were reached because of the high quality of PbI₂ nanosheet with little defect.On the other hand,PbFI photodetectors showed high responsivity mediated by trap states.The novel 2D halide materials with tunable bandgaps,superiordetection performance,and facile synthesis process hold great potential for a wide variety of applications in advanced optoelectronics.?3?By using template method,we made the epitaxial growth of PbS NCs on the surface of PbI₂ nanosheet.PbS NCs layer showed typical p type and mobility of 0.3cm²V^-1s^-1 which was higher than colloidal PbS QDs because there was no ligand on the surface of PbS NCs.The infared photodetector fabricated by PbS NCs showed a responsivity of 22 A/W higher than PbS QDs.The synthetic PbS NCs had a large size and a narrow bangap broaden the absorption range.The detection wavelength could reach2000 nm.Based on the epitaxial structure,we fabricated the hybrid device with different electrode structure?Au and Ag?.The device with Ag electrode improved the response speed?400?s?and working bandwide?300 Hz?because the schottky junction was introduced between the Ag electrode and channel materials.The build-in electric field could speed up the separation of the photocarries and improve the response speed.In addition,PbI₂ layer with broad bandgap had no dangling bond,which could passivate the surface of PbS NCs and make the transfer interface in high quality.As a high barriers layer,PbI₂ could restrain the darkcurrent efficiently.The rapid short wave infrared detection was achieved by constructing the PbS NCs/PbI₂ hybrid structure and optimizing the electrode.