Study On The Carrier Dynamic Characteristics Of Perovskite-based Photoelectric Device

With the continuous research on photoelectric devices,more and more new structures,materials,and mechanisms have been discovered.The performance of photoelectric devices has been greatly improved,and it is expected to play an indispensable role in many fields such as medical treatment and communications,etc.However,the performances of photoelectric devices are still restricted by many factors such as optics and electricity,etc.To further improve the performances of photoelectric devices,it is necessary to quantitatively analyze the multi-physical coupling mechanisms within the devices,and explore the physical mechanisms of carrier transportation and energy loss.From the perspective of optics and carrier transport dynamics,this thesis constructs device-level optoelectronic theoretical models for two common perovskite-based photoelectric devices(solar cells and photodetectors),with the purposes of quantitatively analyzing the multiphysical loss mechanism and clarifying the carrier and ion dynamic characteristics in detail,which is expected to provide a new guidance scheme for the optimization for the highperformance photoelectric devices.The main research results of this thesis are as follows:(1)Hysteresis regulation and performance optimization of perovskite solar cells(PSCs):Research shows that the anomalous hysteresis effect still exists in PSCs,which seriously affects the photoelectric performance and stability of devices.In order to explore the physical mechanism behind the hysteresis effect and the effect of ion migration on carrier dynamic characteristics,this thesis constructs a photoelectric model of PSCs,which can demonstrate the carrier and ion dynamic characteristics in detail.Furthermore,this thesis analyzed the physical mechanism of ion migration by exploring the influence of external bias,ion concentration,doping concentration and energy level of transport layers on the hysteresis effect of PSCs.Based on the photoelectric simulation,multi-optimization strategies are provided for the preparation of high-performance and low-hysteresis perovskite devices,achieving a significant improvement in the reverse(forward)efficiency of the prepared PSCs from 20.81%(17.72%)to 23.35%(22.22%)with the hysteresis index(HI)is dropped to 4.8%.(2)Response time mismatch and performance optimization of perovskite photodetectors(PDs):Self-driven heterojunction PDs can transport carriers by virtue of their built-in electric field without additional bias.However,the reported response time of self-driven heterojunction PDs is usually in microseconds or milliseconds,obviously longer than the commercialized PDs.To address this problem,the intrinsic physical mechanisms within the heterojunction PDs have to be uncovered.Here,a comprehensive photoelectric simulation is implemented to examine the transient response of perovskite PDs based on ni-p structure,where the dynamics of both carriers and ions are taken into account.The mismatched transient responses between the photogenerated electrons and holes,which caused by the different electron/hole transport speeds and asymmetric electric field distribution within the device,are found to severely limit the overall response speed.By further exploring the influences of perovskite thickness,ion accumulation,doping concentration of transport layers on the mismatched time response,a roadmap for improving the response speed of the perovskite PDs is proposed,which shows the greatly shortened response time from 118.21 ns to 7.45 ns.In conclusion,this thesis explores the carrier and ion dynamic characteristics,demonstrates the physical mechanisms of hysteresis effect and response time mismatch,and quantizes the multi-physical loss mechanism by constructing a detailed multi-physical coupling model of perovskite optoelectronic devices.Furthermore,the effective regulation of hysteresis effect and response time mismatch is realized by exploring the influence of electrical parameters on the carrier and ion dynamic characteristics,providing theoretical guidance for the preparation of high-performance perovskite photoelectric devices.