The Wide Bandgap Perovskites Based Ultraviolet Photodetectors

Ultraviolet(UV)photodetectors have attracted much attention for their wide applications in civilian and military fields.Wide bandgap inorganic semiconductor—zinc oxide(Zn O)could be fabricated with low-cost methods,and have emerged as a promising candidate for UV detection and imaging.Nevertheless,Zn O based homojuction photodetectors have been rarely reported owing to the instability of p-type Zn O.Combing organic semiconductor materials with Zn O can effectively solve this issue.However,this type of photodetectors usually suffers from the relatively low responsivity,due to the inferior charge transport properties.Metal halide perovskite have been widely used in many high-performance optoelectronic devices due to their brilliant properties,such as bandgap adjustability and large carrier mobil-ity.Furthermore,chlorine based organic-inorganic hybrid perovskites with suitable band gap have been introduced for UV photodetection.However,efficient UV photodetectors based on inorganic perovskites have been barely reported due to their poor solubility.To solve those problems,we incorporated the CH₃NH₃PbCl₃quantum dots(QDs)with high carrier mobility into thick organic semiconductor layer to enhance the film charge trans-port properties and device performance.Besides,we also investigated the possibility of re-placing organic layer directly by inorganic perovskite as the active layer in UV photodetectors.The key elements of this thesis is as follows:1.CH₃NH₃PbCl₃perovskite QDs prepared via supersaturated recrystallization were doped into Poly(triarylamine)(PTAA)organic semiconductor films.With proper doping amount of CH₃NH₃PbCl₃QDs into PTAA,the responsivity of the UV devices could be in-creased without distinct change of the dark current density,and the specific detectivity of photodetectors could be improved as well.Furthemore,the hole mobility of doped PTAA was determined to be enhanced,that may facilitate the charge transport,and result improved device performance.In addition,the great long-time stability and flexibility of these devices also be demonstrated.2.Cs PbCl₃films fabricated by vacuum thermal-evaporation was employed in UV pho-todetectors.It was found that as the annealing temperature increased,the crystal size of Cs PbCl₃increased and the crystallinity of films was also enhanced.The external quantum efficiency of UV photodetectors based on Cs PbCl₃films increased from blow 5%to around20%,which is in line with the improved morphology and the crystallinity.However,after annealing at higher temperature,the dark current density of the UV devices based on Cs PbCl₃films deteriorated remarkable.It was attributed to the decreased interaction of cesium/acetate(which can effectively passivate traps of Cs atoms in inorganic Cs PbCl₃perovskite films),with the increasement of annealing temperature.The study on thermal evaporation of Cs PbCl₃films and UV photodetectors may also benefit other optoelectronic applications in the future.