Simulation Study On Transport Characteristics Of Photon-generated Carrier In CdSe Quantum Dot Thin Films

The semiconductor quantum dot material has been widely used in energy materials and luminescent devices due to its unique quantum limiting effects and photoelectric properties.The study of carrier transport characteristics in quantum dot thin films provided effective theoretical guidance,for designing the structure and promoting performance of quantum dot thin films photoelectric devices.Recently,in view of the quantum dot thin films carrier transport,the theoretical studies of the space-time distribution of carriers were still lacking.TOF experiment can only get the global current signal brought by carrier transport,not make a concrete analysis of carrier transport and interface charge transfer process in different transport layers.In this paper,the main study was carrier transport process in the CdSe quantum dot thin films,using the continuity equation in the semiconductor,current equation and jumping rate equation theory.The main contents were as follows:Firstly,based on the jump model,three physical fields can be coupled with the PDE module in COMSOL finite element software.The first one was used to study the fluxing and transfer of the carrier in ideal conditions,according to the diffusion and drift motion of carrier.The second indicated the process of trapping and releasing the carrier,which was used to study the transport of carriers under the trap effect.The third was for the interfacial charge transfer process of the surface heterojunction,which is used to study the interface charge transfer process of different sizes of quantum dot thin films.Secondly,according to the material properties of the actual quantum dot films,the carrier transport process in single size quantum dot films was studied.Under ideal conditions,the diffusion motion of the carrier increased the duration of TOF signal,and the drift motion determined the peak of the signal.In the presence of traps,the simulated TOF signal was consistent with the experimental signal,indicating that there was a trap trapping or releasing charge during the actual carrier transport.The traps caused the asymmetry of the carrier diffusion motion,and increased the duration of TOF signal duration.Finally,the interfacial charge transfer process between different sizes of quantum dot films was simulated.The energy level matching structure on both sides of the interface determined the rate of interface charge transfer.The peak of TOF signal was affected by the rate of interface charge transfer.At the same time,the rate of interfacial charge transfer was related to the intensity of the applied electric field.