Self-decoupled tetrapodal perylene molecules for luminescence studies of isolated emitters on Au(111)

Abstract

Self-decoupled tetrapodal perylene molecules were designed, synthesized and deposited on the Au(111) surface through electrospray ionization technique. Photoluminescence and lifetime measurements show that the chromophore groups of the designed molecules are well decoupled from the gold substrate. Molecule-specific emissions from both neutral and anionic molecules were observed in the preliminary electroluminescence measurements. The

Synthesis and Surface Behaviour of NDI Chromophores Mounted on a Tripodal Scaffold: Towards Self‐Decoupled Chromophores for Single‐Molecule Electroluminescence

“…Apparently, the local surrounding has a significant influence on both the electroluminescence efficiency and the energy of the emitted light. In agreement with the recent study on PDI tripodal molecules, [33] the molecular configuration seems to be easily influenced by the nearby tip which hampers reproducibility of STML experiments. The wavelength shift of the substituted NDI molecules compared to the unsubstituted chromophore as it is observed in our PL measurements, does not translate to a shift of the electroluminescence photon spectra of the molecules deposited on the Au(111) surface.…”

“…In addition, both peaks emerge at the same bias voltage, which indicates that the redshifted peak can be attributed to the same molecular transition with an additional excitation of a molecular vibration, [26,60] eV=hν+ħω . Indeed, most photon spectra recorded on the unordered clusters of Tpd‐hNDI show a series of peaks with a typical spacing of about 160 meV (see also Figure S34c), in full agreement with a recent study on tetrapodal perylene diimides (PDIs) on Au(111) [33] . Rarely, light emission above the quantum threshold has been observed, even at low currents, which is an indication for intramolecular up‐conversion (Figure S34b) [61] …”

“…Indeed, most photon spectra recorded on the unordered clusters of Tpd‐hNDI show a series of peaks with a typical spacing of about 160 meV (see also Figure S34c), in full agreement with a recent study on tetrapodal perylene diimides (PDIs) on Au(111). [33] Rarely, light emission above the quantum threshold has been observed, even at low currents, which is an indication for intramolecular up‐conversion (Figure S34b). [61] …”

“… [30] Alternative, less explored strategies to electronically decouple organic emitters from the underlying surface involve either bulky spacer groups within the tailor‐made molecule or large multipodal platforms. [ 31 , 32 ] The latter has been recently applied for example with a fully symmetric tetrapodal molecule, from which three functional arms served as tripod and the fourth arm was perpendicularly arranged in an upward direction, [33] or by separating the chromophore subunit with a rigid multipodal anchoring scaffold. [ 34 , 35 , 36 ] The modular strategy of electronically decoupling via a rigid multipodal platform not only enables the investigation of a variety of chromophores, but also allows to align the chromophore's dynamic dipole vector perpendicular to the surface resulting in enhanced luminescence.…”

2D host–guest supramolecular chemistry for an on-monolayer graphene emitting platform

“…More generally, the electronic decoupling from a metal substrate is usually achieved by self-assembling three-dimensional (3D) functional tectons, [13,14] in order to elevate the molecular functionality from the surface, along its normal direction. On the other hand, controlling the orientation of the photosensitive moieties along a preferential direction, for example to align transition or permanent dipole moments, is another issue.…”