Study On Photodetector Based On Layered Material Quantum Dots/Graphene Composite Structure

Graphene has excellent electrical,optical,and mechanical properties and graphene-based photodetectors have been developed rapidly.However,the low absorbance formed by the atomic thickness of graphene and lack of gain mechanism limits the performance of graphene-based photodetectors.Quantum dots have the advantages of high absorption and tunable band gap.The layered material quantum dots/graphene composite structure can not only improve the light absorption of graphene,but also show good charge separation ability.Liquid phase probe sonication stripping technology has promoted the preparation of layered material quantum dots with unique characteristics.In order to obtain uniformly distributed quantum dots,organic solvents are often used,but the chemical groups of organic solvents may cover the surface of quantum dots and hinder charge transfer,which limit the application of layered material quantum dots in graphene-based photodetector.In this paper,we optimized synthesized process,and got Sn Se quantum dots dispersed in deionized water/ethanol and SnSe₂ quantum dots in deionized water.We demonstated a multi-wavelength response photodetector based on Sn Se quantum dots/graphene composite structure.The wavelengths of 405 nm,532 nm,and 785 nm with the same power were used to illuminate the channel of the device respectively.The maximum response of the device can reach 1.5×10⁷ mAW^-1 under 405 nm light irradiation.Under the illumination of 785 nm,the fastest rising response time of the device is 9.5 ms.We also demonstated ultraviolet photodetectors based on SnSe₂ quantum dots/graphene composite structure on silicon and PET flexible substrate.The channel of the device was irradiated with 405 nm light at different powers.The maximum responsivity of silicon-based devices under 405 nm light irradiation is 7.5×10⁶ mAW^-1,and the rising response time is 0.31 s.The response time of the PET flexible substrate device is 0.26 s and its maximum responsivity can reach 1.8×10⁶ mAW^-1.After bending for 100 times,the responsivity decreases to 1.5×10⁶ mAW^-1,the performance of the detector is relatively stable.The heterostructures between monolayer graphene and QDs improved the light absorption and the transportation of photocarriers,which could greatly increase the photoresponsivity of the device.