Preparation Of Novel Inorganic Oxide Thin Film Heterojunction Based On BiFeO₃ And Corresponding Study Of Optoelectronic Properties

Low-carbon environmental protection gradually becomes a theme of our current era,which globally triggers the growing demands for neo-type energy materials.At present,the conventional silica-based materials still predominate the field of optoelectronic devices,the drawbacks of which including intrinsic brittle and bulky features,energy-intensive production and high costs will,however,make them fall behind the development of“internet of things”as well as wearable micro-/nano-devices calling for high level of integration.Therefore,it is necessary to explore novel pollution-free,low-cost materials with good photoelectric conversion performance.Today,visible light photodetectors are one of the most important components in optical communication networks,environmental sensing,data storage,and so on.Among them,the ferroelectric oxide BiFe O₃（BFO）has received extensive attention due to its lead-free environmental protection,multiferroity and excellent photoelectric properties.In this thesis,we aimed to further improve the photoelectric detection performance of BFO-based thin-film heterojunction in visible light band.Firstly,the bottlenecks that BFO-based photodetectors should break through have been expounded.Then,based on machine learning（ML）calculations,several potential cations were selected to partially replace Fe site of BFO in order to optimize the photoelectric properties of thin films.Thirdly,the in-depth study of the photoelectric detection performance of BFO-based thin-film heterostructure has been done by selecting the suitable hole transport materials.Besides,a three-layer laminated-plate structure has been constructed by coupling the reduced graphite oxide（RGO）,trying to investigate the influence of two-dimensional（2D）materials on photo-response of BFO-based heterojunction.The innovative points of our research are listed as follows:（1）Machine learning has been used to assist the experimental synthesis.Specifically,several noble metal elements including Ir,Pd and Rh have been predicted through ML,and demonstrated to be potential candidates as Fe-site doping elements in BFO to improve the photoelectric conversion performance of BFO.Based on this theory,BiFe_1-xPd_xO₃（BFPO）thin films were prepared and their superior visible light response characteristics were verified.The experimental results showed that Pd doped BFO can regulate the oxygen vacancy concentration of BFO and inhibit the oxidation of Fe³⁺.The optimal photocurrent rise（τ_r）and decay（τ_d）response time constants can reach to 11.16 ms and 8.43 ms,respectively.（2）Visible light photodetector with three-layer thin film stacked structure BFO/NiO/RGO was synthesized by coupling NiO as the hole transport layer.It indicated that 2D RGO can contributes to promote the charge collection and the photoelectric response performance of BFO/NiO/RGO structures.The optimizedτ_randτ_d decreased to 16.01 ms and 11.76 ms,respectively.The performance was ahead of BFO-based counterparts,which would lay a good foundation for realizing high-speed detection for visible light.