Fabrication Of Low Dimensional Semiconductor Materials For UV/Visible Photodetectors Application

Photodetectors can be divided into UV detectors,visible detectors and infrared detectors according to the working band.Ultraviolet and visible photodetectors have been applied in various fields,including space communication,environmental monitoring,and military reconnaissance.Although UV and visible photodetectors have great application potential in the market,it has seen a slower progress up to now.In this thesis,the ultraviolet photodetector based on wide band gap semiconductor TiO₂ and the visible light detector based on perovskite FA_0.85Cs_0.15PbI₃ are studied.The main results are as follows:1)A sensitive ultraviolet photodetector was constructed by simply transferring single-layer graphene on rutile titanium oxide cubic nanorod?TiO₂NRs?array.The cubic TiO₂NRs array was grown on fluorine-doped tin oxide?FTO?glass through a hydrothermal approach.The as-assembled UVPD was very sensitive to UV light illumination,but virtually blind to white light illumination.The responsivity and specific detectivity were estimated to be 52.1 A/W and 4.3×10¹² Jones,respectively.What is more,a wet-chemistry treatment was then employed to reduce the high concentration of defects in TiO₂NRs during hydrothermal growth.It was found that the UVPD after treatment showed obvious decrease in sensitivity,but the response speed?rise time:80 ms,fall time:160 ms?and specific detectivity were substantially increased.The totality of this study shows that the present SLG/TiO₂NR/FTO UVPD may find potential application in future optoelectronic devices and systems.2)A high-performance photodetector comprised of FA_1-xCsxPbI₃ thin film was developed.The Cs doped FAPbI₃ perovskite material was synthesized through a simple spin-coating method,via which FA_1-xCsxPbI₃ with different Cs doping levels?x=0.1,0.15,0.2,0.3?could be obtained.Further optoelectronic characterization reveals that the FA_0.85Cs_0.15PbI₃ photodetector exhibits reproducible sensitivity to irradiation with wavelength in the range from 400 nm to 750 nm,whereas it is weakly sensitive to wavelength longer than 750 nm.The responsivity and specific detectivity were estimated to be around 5.7 A/W and 2.7×10¹³ Jones,respectively.In addition,the LDR is around 76.3 dB.It is also worth noting that the present perovskite photodetector demonstrates an ultrafast response speed?t_r/t_f:117 ns/148 ns?at 3 bias voltage,which is probably related to the relatively high electron mobility,low trap density according to our Hall effect study.Lastly,this device shows a weak decay in sensitivity to white light after storage at ambient condition for 45 days.The totality of broadband sensitivity,high specific detectivity,ultrafast response speed,and self-driven property render the FA_1-xCsxPbI₃ a potential candidate for high-performance photodetectors application.