Interlayer Charge Transfer Coupled with Acoustic Phonon in Organic/Inorganic van der Waals Stacked Heterostructures: Self-Assembled Pt(II) Complex on a PtSe₂ Monolayer

Abstract

Interlayer charge-transfer (CT) excitons in heterostructures are of great importance because of their crucial roles in manipulating the device performance and many-body quantum behaviors. Nonetheless, enigmas arise in organic/inorganic heterointerfaces because localized excitons and inhomogeneity in organic materials hinder the interlayer CT processes. Here, we demonstrate that the interlayer CT excitons form in the new organic/inorganic heterostructure composed by the Pt(II) complex 4Me and monolayered transition-metal dichalcogenide PtSe 2 . The "edge-on" alignment of 4Me is resolved by high-resolution transmission electron microscopy and grazing-incidence X-ray diffraction. Photoelectron spectroscopies verify that the interlayer CT was promoted by the type-II energy band alignment. Moreover, steady-state vis/NIR spectroscopy captures the interlayer CT optical transition and transient absorption spectroscopies unveil the fast charge separation (0.4 ps) coupled with the out-of-plane acoustic phonon mode (0.40 THz) from the PtSe 2 monolayer, followed by the slow charge recombination (0.86 μs). This work systematically characterizes the morphology of the 2D heterointerface and the photophysical mechanism of interlayer CT processes, which expand the vision of the material design in organic/inorganic heterostructures and monolayer-based devices.

Efficient Near-Infrared Luminescence of Self-Assembled Platinum(II) Complexes: From Fundamentals to Applications

“…Moreover, by replacing the py-fpm with fused py-fqz, the delocalization length of Pt­(py-fqz) 2 increases to N = 8.5 (∼3 nm) . In addition, the exciton binding energy of aggregated Pt­(II) complexes is around 0.26 eV, which indicates the formation of CT exciton. , Note that the binding energy of CT exciton is smaller than that (∼1 eV) of the Frenkel exciton, consistent with the occurrence of significant exciton delocalization. Interestingly, the emission wavelength seems to positively correlate with the delocalization length; that is, the longer the delocalization is, the more bathochromic is the emission wavelength.…”

“…Moreover, by replacing the py-fpm with fused py-fqz, the delocalization length of Pt(py-fqz) 2 increases to N = 8.5 (∼3 nm). 4 In addition, the exciton binding energy of aggregated Pt(II) complexes is around 0.26 eV, 34 which indicates the formation of CT exciton. 35,36 Note that the binding energy of CT exciton is smaller than that (∼1 eV) of the Frenkel exciton, 35 consistent with the occurrence of significant exciton delocalization.…”

Low-energy intralayer phonon assisted carrier recombination in Z-scheme van der Waals heterostructures for photocatalysis

“…An intentionally designed heterostructure would excite novel interfacial vibrational patterns and rectify the coupling with charge carriers, thus effectively manipulating charge separation and recombination across the interface. 20,21 Recent work demonstrated that charge recombination in the MoSe 2 /WSe 2 heterostructure is promoted by the heat-driven intralayer shear and breathing modes in the low-frequency region. 22 Thus far, the understanding of the nonradiative scattering across a Z-scheme heterostructure for photocatalysis is still lacking.…”

Molecular Aggregates Associated THz Coherent Vibrations Contribute to Enhancements of Emission Efficiencies

“…7,14,15 Recently, due to rapid advances in materials science, VC in the solid phase has been investigated, and the impact of VC on optoelectronic devices has received considerable attention. [16][17][18][19][20][21][22][23][24][25] Several studies have proposed that VC may assist photoinduced charge separation in photovoltaic materials, 16,18,25,26 although the correlation between VC-assisted charge separation and device performance is still unknown. 17,27 Despite fundamental and technical difficulties, this emerging field has considerable potential and various unexplored topics.…”