Study On Highly Sensitive,Highly Stable,Broad-spectrum Photodetectors Based On Tin-lead Perovskite

Photodetector is a kind of device that converts optical signals into electrical signals.It plays an important role in military,industrial inspection,and national economic fields.In particular,near-infrared light photodetectors also play an important role in various emerging application field such as medical imaging,detection systems and infrared remote control.Organic-inorganic hybrid perovskite materials have some advantages,such as solution preparation,low cost,simple operation,and compatibility with flexible substrates.It is expected to replace traditional optoelectronic photodetectors who have the complicated and expensive manufacturing process.The important thing is that the organic-inorganic hybrid perovskite material also has excellent photoelectric properties such as high light absorption coefficient,high carrier mobility,long exciton diffusion length,tunable bandgaps,which creates a superior prerequisite for the realization of the high-performance devices.However,due to the bandgap limitation of organic-inorganic hybrid perovskite materials,the response of the near infrared cannot be detected.Using Sn²⁺to partially replace Pb²⁺can reduce the bandgap of perovskite materials and effectively solve the problem that lead-based perovskites cannot cover the near-infrared band.However,the Sn²⁺easily oxidized to Sn⁴⁺,and the Sn-based perovskite material has disadvantages such as poor film-forming properties and many defects.This thesis addresses some of the problems that still exist in the perovskite photodetectors field,mainly carry out the following two aspects of research work.First,the selected(FASn I₃)_0.6(MAPb I₃)_0.4tin-lead blend perovskite materials extend the spectral response to 1050 nm.But because Sn²⁺is easily oxidized,the prepared device is extremely unstable.Therefore,we designed a three-dimensional/two-dimensional structure,which greatly improved the stability of the photodetector,and the EQE of the device remained almost unchanged within 70hours.Meanwhile,the structure exhibits excellent passivation effect.The dark current density of the device at-0.1 V as low as 4.6×10^-5m A cm^-2,high special detectivity(D^*)of 1.25×10¹¹cm Hz^-1/2W^-1.The response speed is as fast as 14.66 ns.In addition,this research also applies the device to the imaging field,showing strong practical value.Second,in order to improve the response of the photodetectors in the near-infrared spectrum,we adjusted the Sn and Pb components,and on this basis introduced the doping of Cs cations.The stability of the device cannot be ignored.therefore,the double-sided interface engineering is innovatively proposed in this part of the research.By covering the top of the perovskite film with a two-dimensional structure and passivating the defect at the bottom,the sensitivity and stability of the photodetectors are effectively improved.The double-sided passivation layer has the characteristics of defect passivation for improving charge transport and block water and oxygen for enhancing device stability.The noise value at 70 Hz as low as5.36×10^-13A Hz^-1/2;The D^*value is 2.07×10¹¹cm Hz^-1/2W^-1;the devices stability over 240 h.And the photodetectors show a flat EQE value of nearly 80%in the entire spectral range(300-1050 nm).Finally,the Sn-Pb wide-spectrum photodetectors are integrated into the infrared up-conversion system to realize the application of near-infrared light visualization.This paper is not only have completed the above experimental work,but also analysis theoretical of the above work with in-depth.Improve the stability and detectivity of tin-based perovskite,and practically solve the problems existing in tin-based perovskite photodetectors.It provides new research ideas and methods for the next step of perovskite photodetectors.Finally,combining the advantages of the photodetectors to design and completing the corresponding functional application,it has an important leading significance for the development of the photodetector field.