High Vertical Carrier Mobilities of Organic Semiconductors Due to a Deposited Laid-Down Herringbone Structure Induced by a Reduced Graphene Oxide Template

Abstract

High vertical carrier mobilities in organic semiconductor films are a challenging issue for fundamentally improving the performance of vertical devices. To achieve improvement in the vertical direction, a reduced graphene oxide (rGO) template is used with pentacene and DNTT having a herringbone structure enabling two-dimensional (2D) transport in comparison with CuPc having a slipped-stack structure. A thin-film structure and the optoelectrical properties of the oriented films are investigated with respect to molecular structures and packing modes. The rGO template induces a “laid-down” herringbone structure for pentacene and DNTT with a face-on orientation. Our results reveal that intermolecular dispersion energy is an additional important factor to form face-on states of molecules and influences face-on ratios in the films on rGO. Vertical charge mobilities of the films are significantly enhanced by the rGO template. Particularly, the DNTT film with a laid-down herringbone structure produces a vertical mobility as high as 0.27 cm2 V–1 s–1, one of the highest values for ordinary thin films with several hundred nanometer thickness. These findings suggest that 2D transport is advantageous for vertical carrier transport also.

Performance Improvement with an Ultrathin p-Type Interfacial Layer in n-Type Vertical Organic Field-Effect Transistors Based on Reduced Graphene Oxide Electrode

“…The detailed process of the SCLC method was described in our previous report. 35 The calculated vertical electron mobility of the PTCDI-C 8 was 1.14 × 10 −3 cm 2 /(V s). Under this mobility, the theoretical current density of the PTCDI-C 8 layer was more than 400 mA/cm 2 at a voltage of +5 V, which was 3 orders of magnitude higher than that of the normal rGO-VOFETs (0.73 mA/cm 2 ).…”

“…To investigate whether the current density of the device is limited by the carrier mobility, we evaluated the vertical electron mobility of the PTCDI-C 8 layer using the space-charge-limited current (SCLC) technique (Figure S1). The detailed process of the SCLC method was described in our previous report . The calculated vertical electron mobility of the PTCDI-C 8 was 1.14 × 10 –3 cm 2 /(V s).…”

Controlling Molecular Orientation of Small Molecular Dopant-Free Hole-Transport Materials: Toward Efficient and Stable Perovskite Solar Cells

“…Considering the fact that most efficient dopant-free HTMs contain large π-conjugations, it is straightforward to introduce π-conjugated interfacial materials as templates that can induce face-on orientation via strong π-π interactions with HTMs. For example, the templating effects of graphene materials have been demonstrated for different molecules, such as pentacene, DNTT, and copper phthalocyanine [ 117 , 118 , 119 ]. In addition, graphene materials are widely used interfacial materials in PSCs, and their functions including defect passivation and charge transport optimization have been well demonstrated [ 120 ].…”

Morphology Determines an Efficient Coherent Electron Transport for Push–Pull Organic Semiconductors Based on Triphenylamine and Dicyanovinyl Groups

“…The higher charge transmission of compound 4 with respect to compounds 1 through 3 may be due to its herringbone arrangement ( Figure 4 ). It was previously mentioned that a herringbone structure improves electrical conduction [ 23 ]. In this study, intermolecular charge transfer was enhanced using two-dimensional spatial paths.…”