Mastering the Charge Transfers and Trapping Dynamics in Hybrid Nano-Perovskite/TMDC 2D Photodetectors – MaTra2D

Hybrid interfaces between nanocrystal (NanoX) perovskite materials and two dimensional (2D) transition dichalcogenides (TMD) hold great promises for the development of smart photodetector devices, for they combine two class of model materials displaying exceptional and complementary opto-electronic properties. The low dimensionality of electric field tunable TMDCs and the broadband detection brought by the NanoX provide an ideal platform for smart detectors. However, achieving balanced photo-detection performances, i.e. fast photo-switching and high gains, remains a challenge and the time-response of most NanoX-perovskite/TMD photodetectors operating in the visible part of the spectrum remains in the best cases limited to the ms range. To achieve better performances, it is mandatory to achieve an optimal balance between the effective photocarrier lifetime (directly related to the trapping time constant) and the carrier transit time between the electrodes of the device; it is also critically important to master the band alignment and the built in electric fields at the perovskite/TMD interfaces.
In MaTra2D, our goal is to implement a rational approach for understanding and mastering all the processes that will ultimately determine the performances of hybrid photodetectors, realized by sensitizing TMDs with perovskites nanocrystals and nanoplatelets. This approach encompasses the synthesis and processing of high quality TMD films, the synthesis of perovskites nanocrystals/nanoplatelets along with a suitable ligand engineering, the systematic use of complementary advanced photo-physical characterization methods, and the fabrication of field effect photo-transistor devices with an improved dielectric interface. The experimental characterizations will cover a large range of complementary techniques: photoluminescence (PL), cathodoluminescence, Raman spectroscopy, photoelectron spectroscopy, Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy (KPFM). One highlight of MaTra2D will be to systematically use advanced potentiometric and electrostatic modes derived from the atomic force microscope to probe the nature of the built-in electric fields at the perovskite/TMD interfaces, the photo-induced charge transfer mechanisms (by differential surface photovoltage imaging), and the trap-release dynamics and carrier dynamics in the active device channel by time-resolved surface potential and photovoltage imaging. Thanks to this “near field” approach without equivalent in the literature, we should be able to predict if a given perovskite/TMD interface has the potential to achieve a fast photoswitching, prior to characterizing the performances of the full operating device by macroscopic photo-transport measurements. Such a predictive approach will be quite useful to screen more efficiently the potential of new hybrid perovskite/TMD interfaces for photodetection.