Study On Mixed Halide Inorganic Perovskite Photodetectors Based On CsPbI₂Br

All inorganic metal halide perovskite shows great application potential in the field of photoelectric devices due to its excellent physical and chemical properties,such as ultra-high quantum yield,high absorption coefficient,large carrier mobility,bipolar carrier transport capacity,high stability and simple synthesis schemes.Considering the balance of light absorption capacity,band gap width and phase stability,mixed halide inorganic perovskite is considered as an ideal photoactive material.Among them,CsPbI₂Br has a suitable bandgap width and good stability,making it a photosensitive material for photodetectors.However,the defects in CsPbI₂Br perovskite thin films and the low energy level matching between CsPbI₂Br and electrodes limit the performance of CsPbI₂Br photodetectors.Therefore,optimizing the material preparation scheme and device structure is of great significance for improving the performance of CsPbI₂Br perovskite photodetectors.This paper constructs heterostructures of CsPbI₂Br thin films with CsPbBr₃ quantum dots and Ag₂S quantum dots,respectively,to improve the energy level matching between CsPbI₂Br and electrodes,reduce non radiative recombination of charge carriers,and thereby enhance the performance of CsPbI₂Br perovskite photodetectors.In addition,by adding CsBr and H₂O to the precursor solution of CsPbI₂Br,the quality of CsPbI₂Br thin films is improved,the requirements for environmental conditions during device preparation and testing are reduced,and the photoelectric conversion ability of CsPbI₂Br photodetectors is improved.The construction of heterostructures and additive passivation strategies provide solutions for improving the quality of perovskite materials and improving the detection performance of perovskite photodetectors.The main research contents of this paper are as follows:1.A high response perovskite photodetector with CsPbBr₃/CsPbI₂Br layer heterojunction was prepared by solution method.As a sensitizer,CsPbBr₃ can improve the light absorption capacity of the device.Due to the different energy levels of CsPbBr₃ and CsPbI₂Br,layer heterojunction is formed,so as to construct bipolar carrier transport channel and improve carrier transmission performance.At 405 nm,the CsPbBr₃/CsPbI₂Br layer heterojunction photodetector showed a high responsivity（R）of 66 A/W,a specific detectivity（D*）of 1.17×10¹¹ Jones,and a rise/fall time of38/81 ms.This work provides a feasible strategy for preparing layer heterojunction perovskite devices.2.The Ag₂S/CsPbI₂Br bulk heterojunction photodetector is studied.By adding Ag₂S quantum dot aqueous solution to CsPbI₂Br perovskite precursor,film defects are passivated and the quality of perovskite films is improved.Moreover,the construction of Ag₂S/CsPbI₂Br bulk heterojunction optimized the energy level arrangement between CsPbI₂Br and gold（Au）electrodes,improving the carrier transport ability.This comprehensive strategy improves the performance of perovskite photodetectors.The Ag₂S/CsPbI₂Br bulk heterojunction photodetector has an ultra-low dark current of 7.74 p A,an ultra-fast response time of 2.95/3.07μs and a high switching ratio of7.67×10⁵.This work provides a method for the preparation of high quality perovskite materials and a strategy for the development of high performance perovskite photodetectors based on bulk heterojunction.3.High performance CsPbI₂Br photodetectors enhanced by excess CsBr and a certain amount of H₂O are studied.Excess CsBr helps to generate micro-strain in the lattice,thus stabilizing the cubic phase of CsPbI₂Br at low temperature.H₂O molecules fine-regulate the balance of proton transfer reaction in the precursor solution,manipulate the thermodynamic favorable phase by adjusting the size of perovskite microcrystals,reduce the surface free energy,and passivate the film defects.Excess CsBr and a certain amount of H₂O enhanced CsPbI₂Br photodetectors have excellent photoelectric detection performance,with R up to 160 A/W,D*is 4.9×10¹¹ Jones,the response time is 5.5/6.8 ms.This work provides experience for passivation strategies of perovskite optoelectronic devices.