Study On Electrostatic-potential-boosted Self-powered Photodetector

Ultraviolet photodetectors are widely used in many fields such as fire warning and environmental monitoring.Conventional UV photodetectors need external power to provide energy to work,but the self-powered devices developed in recent years can work without external power supplies,which are ideal for building low-energy-consumption and environment-friendly optoelectronic systems and the Internet of Things,thus becoming a current research hotspot.However,high-performance self-powered UV photodetectors are still not available.In this paper,the charge transfer properties of the semiconductor/dielectric interface are investigated theoretically and experimentally,and a new high-performance self-powered UV photodetector with a built-in electrostatic field at the dielectric interface coupled with a conventional semiconductor junction device is developed.The main research contents and results of this paper are as follows:1.Based on the first calculation principle and molecular dynamics simulation,the transferred charges between rutile titanium dioxide（TiO₂）and Poly tetra fluoroethylene（PTFE）molecules are quantitatively analyzed,and it is found that there is a certain charge transfer when the TiO₂and PTFE molecules are separated by 2-4（?）range.At 2（?）,the PTFE molecule with a length of about12×4（?）gains 0.509484 e(e=1.6×10^-19C)of charge and the TiO₂molecule loses the same amount of charge.In addition,based on the coupling of contact electrification and electrostatic induction,the electrical output properties of TENGs composed of TiO₂and PTFE are investigated using triboelectric nanogenerators（TENGs）as probes.The experimental results reveal that at the contact interface between TiO₂and PTFE,the surface of PTFE is negatively charged and the surface of TiO₂is positively charged,and the charge transfer occurs when the two are in contact.Moreover,the charge transfer properties between TiO₂and polydimethylsiloxane（PDMS）are compared and analyzed.It is found that the TENG composed of TiO₂/PDMS has similar properties but about 10 times lower output compared with the TENG composed of TiO₂/PTFE,indicating the electronegativity of the dielectric material is a direct factor affecting the magnitude of charge transfer at the contact interface.2.Based on the charge transfer property between interfaces,the electrostatic charge on the PTFE surface is used to form a built-in electrostatic field to develop a high-performance self-powered photodetector.A self-powered heterojunction UV photodetector with a vertical structure of ITO/TiO₂/PTFE/Cu is designed and fabricated.By improving the preparation process and optimizing the structural parameters,the modulating effect of the dielectric layer on the photodetection performance of the ITO-TiO₂heterojunction is systematically studied.It is found that the PTFE layer plays a dual role in the device:first,it acts as a high-resistance layer to reduce the dark current of the device at zero bias voltage and improve the signal-noise ratio of the device;second,it acts as an electret to provide a stable built-in electrostatic field for the device,which works together with the built-in electric field of the ITO-TiO₂junction to accelerate the diffusion and drift of photogenerated carriers,producing an enhanced photovoltaic effect and improving photodetection performance.The research results show that at zero bias voltage and 365 nm UV light,the responsivity of the device reinforced by PTFE is as high as 76.87 m A/W,the specific detection rate is 4.79×10¹²jones,and the EQE reaches 26.48%.It also exhibits a rapid rise and decay time of 7.44 ms and 3.75 ms.Compared with a conventional ITO/TiO₂heterojunction device without PTFE,the ESPB-SP photodetector demonstrates its photoresponse,light–dark ratio,rise speed,and decayed time improved by 442,8.40×105,111,267 times higher than those of traditional device.Furthermore,the ESPB-SP device exhibits excellent temperature and circumstance stability,with photodetection performance remaining constant over the range of room temperature to 70°C and remaining unchanged for more than 60 days of exposure under air surroundings without packaging.Finally,the effects of different materials and different thicknesses of dielectric layers on the detection performance are systematically discussed.3.Based on the electrostatic potential boosted photovoltaic effect,the self-powered photodetection performance is further improved by applying a polarizing field to the dielectric layer and constructing a TiO₂film surface microstructure.A self-powered UV photodetector with PTFE polarized and surface microstructure is prepared.The research results show that at zero bias voltage,the highest photoresponsivity and external quantum efficiency of the PTFE-polarized device reach 150 m A/W and 49%,respectively.The photoresponsivity of the device treated with the surface microstructure increases to 186.2 m A/W,the external quantum effect reaches 71%,and the response speeds reach1.06 ms/0.36 ms（rise time）and 0.92 ms/0.52 ms（decay time）,respectively,successfully achieving the effective regulation of the electrostatic-potential-boosted effect.The electrostatic-potential-boosted UV photodetector device developed in this paper has the advantages of high self-powered detection performance,good temperature stability,accessibility to fabrication,and environmental friendliness,and is expected to inspire more applications in the future.