Revealing the electronic structure of organic emitting semiconductors at the single-molecule level

Abstract

Revealing the electronic structure of organic emitting molecules is instructive for tuning electron-hole balance, one of the key factors in regulating the organic light emitting diodes (OLED) performance. Herein, we...

Mechanistic Investigation and Conductance Modulation of a Metal‐Molecule‐Metal Junction via Extra Acid Addition

“…For these three junctions, it was speculated that their low‐bias transport is dominated by the LUMO state, which is consistent with the previous studies that organic components terminated by benzonitrile linkers usually show LUMO‐mediated conducting behavior [13] . As we know, the electron‐withdrawing ability of B(C 6 F 5 ) 3 and TfOH can make the electron density more deficient in their benzonitrile linkers, [11d] thus pulling down the LUMOs of DBP−B(C 6 F 5 ) 3 or DBP−TfOH compared with that of the unmodified DBP. By that way, their DFT calculated LUMOs energy levels were brought down from −2.18 eV to −3.01 and −2.67 eV (Figure 2a), resulting in a tunneling barrier (ϵ) of 2.42 eV, 1.59 eV and 1.93 eV with respective to the Au Fermi energy level (E F =−4.6 eV).…”

Developing Longer‐Lived Single Molecule Junctions with a Functional Flexible Electrode

“…A Au‐coated nanopipette electrode (NPE) is used as the tip of a home‐built STM on a gold substrate as described elsewhere. [ 14–17 ] The NPE is fabricated by sequentially depositing chromium and gold on a laser‐pulled quartz nanopipette (see Section S1.1, Supporting Information), and the produced electrode possesses a conducting exterior surface, an open channel and a long shank length (6.1 ± 0.1 mm) with a high flexibility [ 14 ] (k NP ≈ 0.13 N m −1 , see atomic force microscopy (AFM) measurement of the NPE spring constant in Section S2.1, Supporting Information). The optical image of a typical NPE and its SEM images of the tip apex are displayed in the inset of Figure 1a.…”

The effect of non-covalent conformational locks on intra-molecular charge transport of OPV units

“…26 From the diagram, we see that the HOMOs lie closer to the E F rather than their LUMOs, implying that their HOMOs are the dominant charge conducting channels. 26,27 Although there are many uncertainties in such estimates, the qualitative CV-based conclusions that the HOMOs are closer to E F are supported by calculations (see below). In addition, the tunnelling barrier ( ε 0 ) for DT-FBT , DT-BT , and DT-OBT is gradually lowered (Fig.…”

“…3b), and thus the electronic coupling intensity ( Γ ) between the HOMO and E F would increase. 26 According to the single-Lorentzian model: G = G 0 /[( ε 0 / Γ ) 2 + 1], the conductivity trend for the three molecules would be: G DT-OBT > G DT-BT > G DT-FBT . This trend agrees with the experimental findings that DT-OBT yields the highest conductance among the three molecules but displays a reversed trend for DT-BT and DT-FBT .…”