Photoelectric Detection And Photocatalytic Properties Of Heterojunction Piezoelectric Composites

The piezoelectric photonic effect is a three-way coupling effect of piezoelectric,optical excitation and semiconductor properties in non-central symmetric semiconductors.It has great development potential in improving the quantum yield efficiency of photoelectric materials and devices,thereby helping to improve the efficiency of energy conversion and alleviate various energy shortage crises faced by mankind.The construction of heterojunctions can provide a powerful tool for the design of high-performance devices through the band shift occurring at the interface.Therefore,the construction of heterojunction piezoelectric semiconductor materials and the study of piezoelectric photoelectronic effects in heterojunction materials are of great significance to promote the application of piezoelectric photodetection and piezoelectric photocatalysis.Developing new photodetectors with good photoresponse,high stability,flexibility,and minimalization is urgently demanded facing the rapid development of optical technology.In Chapter two,Zn O-Sn O₂ heterojunction nanofibers are synthesized by electrospinning.The flexible UV micro-photodetector is fabricated by combining Zn O-Sn O₂ heterojunction nanofibers with photolithography-patterned Au microelectrodes on PI substrate.An extremely low dark current(～10^-11 A)is obtained due to the formation of Zn₂Sn O₄ layer at the large interface of Zn O-Sn O₂ heterojunctions.Upon exposure to UV light with power density of 24μW cm^-2,the photodetector exhibits high on–off ratio of～10⁴,high responsibility of 267 A W^-1,and fast response speed of 2.75 s.The photodetector has good photoelectric properties and high UV selectivity.Moreover,the flexibility of the UV photodetector is demonstrated.The photoresponse remains～60%of the initial level even under a large bending angle of 45^°.The combined utilization of electrospinning and photolithography is convenient to fabricate flexible UV photodetectors.Sonophotocatalysis is one of the most significant outcomes of the exploration of the interaction between piezoelectric field and charge carriers,which exhibits potential applications in dye degradation,water splitting,and sterilization.Although several heterojunction catalysts have been applied to improve the sonophotocatalytic capability,the importance of the morphology on the sonophotocatalytic capability has not been emphasized.In this study,brush-like Zn O nanorod arrays are synthesized on a stainless-steel mesh and subsequently vulcanized into Zn O-Zn S core-shell nanorod arrays to investigate the sonophotocatalytic capability of the heterojunction.The sonophotocatalytic capability increases from 25.1%to 45.4%through vulcanization.Afterward,the Zn O-Zn S nanorods are etched to Zn O-Zn S nanotubes without affecting the crystallography and distribution of the Zn S nanoparticle shell,further improving the capability to 63.3%.In Chapter 3,The improvement can be ascribed to the coupling effect of the enhanced piezoelectric field and the reduced migration distance,which suppresses the recombi-nation of photoexcited electron–hole pairs while transforming the morphology from nanorod to nanotube,as proven by the electron spin resonance test and numerical simulations.This study explores a novel approach of morphology engineering for enhancing the sonophotocatalytic capability of heterojunction nanoarrays.