Ferroelectric BaTiO₃ Enhances TiO₂ Self-Powered Photodetector Performance And Multifunctional Applications

Self-powered photodetectors can achieve light detection without an external power supply,which is beneficial for miniaturization,integration,and low power consumption of the device.With the development of Io T technology,self-powered photodetectors show important development prospects in the fields of optical communication,machine vision and biomedical imaging.At present,the light detection capability of self-powered photodetectors needs to be further enhanced and their functions need to be expanded to meet the needs of applications in multiple fields.The photovoltaic effect of ferroelectric materials is an effective way to enhance the performance of self-powered photodetectors.In this work,we use ferroelectric BaTiO₃（BTO）to enhance the performance of TiO₂self-powered photodetectors and explore the multifunctional applications of the devices.The main contents are as follows:（1）The surface and defect states of nanostructured photodetector materials act as compound centers for photogenerated carriers,affecting device photocurrents and photoresponse speed.The BTO is modified on the surface of TiO₂nanorod arrays（NRs）by in situ transformation using hydrothermal reaction to passivate the surface defective and defective states of TiO₂NRs.And TiO₂andBTO form a good interfacial contact through Ti-O-Ti bonds,which is conducive to the effective transfer of carriers.The loading of BTO on the surface of TiO₂NRs is regulated by varying the Ba²⁺concentration in the precursor solution.The FTO/TiO₂-BTO/In self-powered UV photodetector device with Ba²⁺concentration of 0.05 M achieves a photoresponsivity of 3.34 mA/W,a photoresponse rise time/fall time of 2.1/1.4 ms,and a photodetection rate of 7.96×10¹⁰Jones.The self-powered TiO₂-BTO photodetection is also used in the light-controlled“and”and“or”gate logic circuits,showing the potential of the device for optical communication applications.（2）Both ferroelectric photovoltaic effect and photovoltaic effect of heterojunction contribute to the performance of self-powered photodetector.Self-powered TiO₂/BTO heterojunction UV photodetectors are constructed with in situ transformedBTO and TiO₂NRs.The BTO thickness and the loss of TiO₂NRs are controlled by changing the conversion time,which in turn modulates the light absorption,carrier concentration,and interfacial transfer resistance of TiO₂/BTO.The device performance of the FTO/TiO₂/BTO/In device with 2 h of BTO conversion is the best.Under 365 nm light illumination,the device has a responsivity of 0.17 A/W,a detectivity of 6.0×10¹²Jones,an LDR of 97 dB and a response improvement in photoresponse speed.The self-powered optical response of the device to polarized light is also used to explore the application in the field of orientation recognition.（3）The ferroelectric polarization electric field is contribute to the separation and transport of photogenerated carriers.The ferroelectric BTO is introduced at the interface of the FTO/TiO₂/CuInS₂/Au self-powered heterojunction device.The amount of BTO and the Cu/In ratio of CuInS₂deposited on the BTO are regulated by changing the BTO conversion time,which in turn changes the absorption characteristics of CuInS₂in the visible region.It is found that the self-powered optical response characteristics of the FTO/TiO₂/BTO/CuInS₂/Au devices with 2 h in situ convertedBTO is the best.The ferroelectric polarization field of BTO with a suitable deposition amount and the interfacial electric field of BTO/CuInS₂are beneficial to enhance the separation ability of photogenerated carriers of the device,promote carrier transport and reduce the chance of recombination.The self-powered optical response characteristics of the device in the visible region are used to explore the application of the array structure for full-color imaging.