Plasmon-enhanced Photoelectric Properties Of Au-PbS Nanostructures And Their Application In Photodetection

With the continuous development of nanoscience,lots of synthetic methods of nanostructures have been developed by researchers.Nanostructures,compared with the corresponding bulk materials,exhibit some unique optoelectronic properties,such as surface plasmon of noble metal?gold or silver?,which has greatly attracted interests in this field.To improve the photoelectric conversion efficiency of devices,the coupling between surface plasmon and exciton in semiconductor has been widely used in optoelectronic devices such as solar cells,photodetectors and photocatalytic anodes.In recent years,a lot of research results indicate that the local surface plasmon resonance generated by metal nanostructures can enhance the local electromagnetic field near the metals.The adjacent semiconductors can benefit from the enhanced field,resulting in an enhanced absorption of light and generating more photogenerated carriers.In addition,the scattering effect,hot carriers transfer and resonance energy transfer also contribute to photoelectric conversion.Therefore,in metal-semiconductor hybrid nanostructures,it is important to make full use of the enhanced field for semiconductors.Herein,we investigate two types of near infrared photodetectors based on Au-PbS core-shell nanorods and PbS quantum dots doped Au nanorods.Compared with single lead sulfide photodetectors,these two devices have improved the performance of photodetection,especially in near infrared wavelength band.The main research work as followed:1.The near infrared photodetector based on PbS quantum dots doped Au nanorods was firstly investigated.With the power density of 5 mW×cm^-2 of 808 nm wavelength laser illumination,the device achieved a responsivity of 8.2 A×W^-1,a detectivity of6.3?10¹⁰ Jones,an EQE of 1251%at the source-drain voltage and gate voltage of-4V,which is 1.7 times,1.3 times,1.6 times than that of PbS quantum dots,respectively.2.Then,the photodetector based on Au-PbS nanorods was investigated.From the absorption spectrum,it was found that the local surface plasmon resonance peak of nanorods shifted from visible to near infrared band as the refractive index increased of the shell.The localized electric field distribution of a single core-shell nanorod was simulated under light illumination by FDTD method.The results show that the local field enhanced up to 22 times.The Au-PbS nanorods based photodetector achieved a responsivity of 18.5 A×W^-1,a detectivity of 1.22?10¹¹ Jones,an EQE of 2844%,characterized by the same conditions with PbS quantum dots doped Au nanorods based photodetector.Compared with the pure PbS photodetector,the responsivity,detectivity and EQE increased 3.8 times,2.5 times,3.7 times,respectively.These results show that surface plasmon of metal nanostructures enhanced photodetection would have great potential application in optoelectronics.