Study On Electric-field-modulate Phase Transition Of Two-dimensional Perovskite

Structural phase transition refers to the property that a material can switch reversibly between at least two different structural states under the influence of external factors near the phase change temperature.Therefore,phase transition materials can be used in a range of fields,such as sensors,data storage and switching devices.Organic-inorganic hybrid two-dimensional perovskites are common structural phase change materials,which have attracted much attention because understanding its structural phase transition is essential for improving the performance of optoelectronic devices.However,studies on the possible mechanism for the phase transition of organic-inorganic hybrid two-dimensional perovskites is still lacking,and the regulation of its structural phase transition is difficult to achieve,which seriously hinders the research and application of devices that use the structural phase transition of organic-inorganic hybrid two-dimensional perovskite structure to achieve unique functions.By designing and preparing two kinds of devices with non injection electric field and charge injection structure based on two-dimensional perovskite（BA）₂Pb I₄,how the external electric-field modulates the structural phase transition was studied.The external electric field can promote the structural phase transition to the dominant phase in both structures,and the non-injected electric field exhibits a larger degree of modulation.Through further analysis,it is concluded that the reason of electric field regulating the structural phase transition in（BA）₂Pb I₄ might be that the electric field releases the stress produced by the two-phase competition in the process of structural phase transition,and then promotes the phase transition.Base on the above conclusion,we further studied how the electric field manipulates the interlayer exciton emission formed between those two phases and monolayer WSe₂.First of all,we have proven that different（BA）₂Pb I₄ structural phases and monolayer WSe₂can form two different kinds of interlayer excitons.（BA）₂Pb I₄/WSe₂/BN/Graphene structure and WSe₂/（BA）₂Pb I₄/BN/Graphene structure were designed and fabricated to investigate how those two sorts of interlayer excitons can be modulated with the external electric field.We found that those two sorts of interlayer excitons in both structures can be effectively tuned by the electric field.In summary,based on the organic-inorganic hybrid two-dimensional perovskite（BA）₂Pb I₄,we have systematically studied how the electric field affects the structure phase transition of two-dimensional perovskite and revealed the underlying mechanism.Furthermore,based on the structural phase transition,the effect of electric field on the interlayer exciton in（BA）₂Pb I₄/WSe₂heterostructure was investigated.Our studies not only play a significant role in understanding the structural phase transition properties of two-dimensional perovskites,but also provide a perspective for device design and performance improvement based on structural phase transition of two-dimensional perovskites.