Ioannis Leontis is visiting us
Ioannis Leontis carried out his PhD at the University of Exeter about the “Study of electron transport through graphene homojunctions and optoelectronic characterization of 2D perovskites”. His research topics re a mainly focused on the study of the electrical transport properties of 2D materials and the optoelectronic characterization of 2D materials based nanoelectronic devices. He is currently a post-doc researcher in the Quantum Systems and Nanomaterials (QSN) Group at the University of Exeter.
He will talk to us about:
Effect of sub gap traps on the conduction and the photoconduction of 2D F-PEAI metal halide perovskites
Abstract: Due to their unique optoelectronic properties 2D metal halide perovskites (2D MHPs) have been widely used for the fabrication of ultra-sensitive photodetectors (PDs). Sub gap states at the edge of 2D MHPs, known as ”edge states”, have been related with the dissociation of the bound excitons to long life free carriers into this layered structure. In this case, especially after sub gap excitation, edge states dominate photoconductivity of 2D MHPs. However, band-to-band excitation induces photogenerated carriers into the whole volume of the flake and bulk trapping effects are negligible. Despite the fact that the properties of the 2D MHP edge states have been extensively studied trapping effect of carriers into the whole volume of the 2D MHPs is still not clear. In this work we study the effect of carrier trapping at the conduction and photoconduction of the 2D-fluorinated phenylethylammonium lead iodide perovskite (2D F-PEAI). The recently established threshold voltage transient spectroscopy for the characterization of 2D material based FETs is used revealing the presence of sub gap trapping states into the whole crystal the energy depth (ET) of which does not exceed 8.06meV (∆ET ≤ 8.06meV ) confirming the lack of deep trapping effect at RT. Furthermore, temperature dependence photoconduction measurements shows that trapping states affects the photoconductivity of the Au/2D F-PEAI/Au devices. At low temperature deep trapping effect dominates the photoconduction mechanism of the devices inducing photoenhanced space charge limited conduction, while at RT strong unbalanced carriers transport in combination with the blocking contacts introduce space charge limited photoconduction. Finally, the photodetection of the Au/2D F-PEAI/Au structures is also studied showing that an inner photo conductive gain mechanism allows these Schottky-type metal-semiconductor-metal photodetectors to combine both high quantum efficiency and high detectivity.