Preparation Of Crackled Thin Films Of Tin Dioxide/Chalcogenide Semiconductors And Their Photoelectrochemical Properties

Thin films of nano-semiconductor materials have a wide range of applications in the fields of energy,chemical engineering,communications,medicine and others.In this thesis,we study the preparation,characterization,and photoelectrochemical properties of several thin films of semiconductor optoelectronic materials(Sn O2/Cd S,Sn O2/Cd Se and Cd S)with dense reticular micro-nano crackle structures.The main contents are as follows:(1)Thin films of Sn O2 with dense reticular micro-nano cracks were synthesized by dropping sol-gel Sn O2(obtained by refluxing Sn Cl22H2 O ethanol solution ad aging)onto fluorine-doped tin oxide(FTO)conducting glass and heating it at high temperature.The Sn O2/Cd S heterojunction film was obtained by modifying the crackle film with Cd S nanoparticles via successive ionic layer adsorption and reaction(SILAR).The surface morphologies and compositions of Sn O2/Cd S thin films were analyzed by Scanning Electron Microscope(SEM),Transmission electron microscopy(TEM),energy dispersive X-ray spectroscopy(EDX)and X-ray diffraction(XRD).The influence of SIIAR cycles,aging time of Sn O2 sol and sacrificial agents on the photoelectrochemical performance were investigated and discussed.Under optimized conditions,the Sn O2/Cd S film could generate a saturated anodic photocurrent density as high as 10 m A cm-2 under visible light illumination of 100 m W cm 2 in a2 M Na OH + 2 M CH3 OH solution,corresponding to a solar-to-electricity conversion efficiency up to 9.4%.(2)Sn O2/Cd Se heterojunction film was synthesized by modifying the sol-gel derived crackle film of Sn O2 nanoparticles on conducting glass with Cd Se nanoparticles by SILAR.The surface morphologies and compositions of Sn O2/Cd Se thin films were analyzed by SEM,XRD and Raman spectroscopy.The influence of SIIAR cycles and sacrificial agents on the photoelectrochemical performance were investigated and discussed.Photoelectrochemical tests under visible light illumination of100 m W cm-2 show that the Sn O2/Cd Se film could generate a saturated anodic photocurrent density as high as 8 m A cm-2,corresponding to a solar-to-electricity conversion efficiency of 4.08 %.(3)Thin films of Cd S nanoparticles with dense reticular micro-nano cracks were obtained by heating the prepared Cd S film through two steps:transferring a thin film of Cd S nanoparticles assembled at gas/liquid interface onto conducting glass and modifying it with Cd S nanoparticles by SILAR.The surface morphologies and compositions of Cd S thin films were analyzed by SEM and XRD.The effect of sacrificial agents on the photoelectrochemical properties of Cd S films was also investigated.The prepared Cd S film with micro-nano cracks by the combined methods of interfacial assembly and SILAR could generate a saturated anodic photocurrent density as high as 6.4 m A cm-2,corresponding to a solar-to-electricity conversion efficiency up to 11.07 % under visible light illumination of 100 m W cm-2.That was better than those Cd S films prepared by respective method either gas/liquid interface assembly or SILAR.