| Infrared photoelectric detection has a broad application in the fields of meteorological prediction,military reconnaissance,environmental monitoring,and medical treatment,etc.It is one of the research focuses to prepare the self-powered infrared detector with an excellent performance by low cost and mass production.Due to its strong electron transport ability,TiO2 has been used to prepare hot-electron-based infrared photodetectors via combination with metal.However,the absorption of metals to infrared light is poor and the hot-electron current generated in the metal is restricted by the Schottky barrier and defects between metal and TiO2,resulting in a small photocurrent and a slow response rate.Aiming at improving the performance of infrared detectors,this paper constructs TiO2-based composite materials,and adopts various methods to improve the photocurrent,detectivity,on/off ratio,and response rate.Based on this,the main contents of this paper are as follows:(1)Developed a new route to modulate hot-electron photocurrent generated by infrared light(NIR)by ultraviolet light(UV)illumination.Au/TiO2/FTO photodetectors were prepared by the simple sol-gel method.With the aid of UV light,the hot-electron current of NIR can be amplified more than ten times,and the response rate can be greatly improved.It is found that the reduction of the potential barrier by UV light and the trap-filling effect of carriers on defects improve the injection efficiency and transfer of hot electrons.Increasing the power density of UV promotes the hot-electron current to quickly reache a stable state.This provides a simple way to increase photocurrent and response rate of detector.(2)Proposed a new idea to reduce background current and improve on/off ratio by combining UV irradiation and doping rare earth elements.Au/TiO2:Tb3+/FTO photodetectors were prepared by adding Tb3+into TiO2 films.Through the energy and charge transfer between TiO2 and Tb3+levels,the current generated by UV-induced TiO2 interband transition is effectively suppressed,and the background current of the hot-electron current excited by NIR is greatly reduced.Compared with pure TiO2 photodetectors,doping Tb3+increases the detectivity by 6 times and the on/off ratio by about 4,0000 times.(3)Proposed a strategy to improve the photoelectric properties of PbS films by Sn2+ sensitization.Sn2+-sensitized PbS films were prepared by the chemical bath deposition.One can found that Sn2+ sensitization improves the crystallinity,enlarges the grain size of PbS,increases the free carrier concentration,and prolongs the carrier lifetime.Therefore,the responsivity of Sn2+-sensitized PbS photodetector is increased by about 5 times,the detectivity is increased by about 7 times,and the response rate is increased by 105 times.This shows that Sn2+-sensitized PbS films have a high application prospect.(4)Based on the above results,self-powered Au/PbS/TiO2/FTO heterojunction photodetectors were fabricated.One can found that the photocurrent of the detector to NIR can be increased by dozens of times by introducing PbS as NIR absorption layers.As the built-in eletctric field between PbS and TiO2 promotes the separations of photogenerated carriers,the rise/fall time of photoresponse is up to 44 ?s/37 ?s.After 1200 times of switching,the change of photocurrent is less than 5%,suggesting the stability of the detector.This work provides a reference for understanding and designing self-powered heterojunction optoelectronic devices. |
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