Nano-films of carbo-benzene derivatives: Scanning probe microscopy analysis and prospects of use in organic solar cells

• Published in: Synthetic metals 2021-08, Vol.278, p.116826, Article 116826
• Main Authors: Caballero-Quintana, Irving, Rivera-Taco, Julio, Barthes, Cécile, Nicasio-Collazo, Juan, Ramos-Ortíz, Gabriel, Maldonado, José-Luis, Maraval, Valérie, Chauvin, Remi
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; Benzene; Carbo-mers; Chemical Sciences; Electric contacts; Hole mobility; Material chemistry; Microscopes; Microscopy; Monolayers; Organic chemistry; Organic solar cells; Photovoltaic cells; SAMs as hole transport layer; Scanning probe microscopy; Scanning probe microscopy analysis; Self-assembled monolayers; Self-assembly; Solar cells; Substrates; Work functions
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2021.116826

Three carbo-mer derivatives based on a C18Ph4 core decorated with two identical electro-active groups X, i.e. two aromatic carbo-benzenes (1 and 2, X = 4-anilinyl) and one pro-aromatic carbo-quinoid (the carbo-TTF 3, X = 1,3-dithiol-2-ylidene) were studied through Scanning Probe Microscopies (SPMs). Self-Assembled Monolayers (SAMs) were fabricated (thickness ~160 pm), for the two centrosymmetric representatives 1 and 3, the organization of which on the HOPG substrate was found to be structure-specific. Electrical/electronic properties of the three carbo-mers were determined by using Atomic Force Microscopy (AFM) and its electrical modes: Kelvin Probe Force Microscopy (KPFM) and conductive Atomic Force Microscopy (c-AFM). Measurements of the work function (∅) through KPFM result in a ∅ = 5.60 eV value for 1, 4.97 eV for 2 and 4.82 eV for 3. Hole mobility (µ) values extracted from local I-V plots by using c-AFM are 15×10−8cm2V−1s−1 for 1, 3×10−6cm2V−1s−1 for 2 and 87×10−8cm2V−1s−1 for 3. A concept test of the possible application of carbo-mers in self-assembled hole transporting monolayer (SA-HTM), with the view to replacing the most common p-type contact used in organic solar cells (OSCs), PEDOT:PSS, is also reported. [Display omitted] •Analysis of three carbo-mer derivatives by Scanning Probe Microscopies (SPM).•Self-Assembled Monolayers (SAMs) and very thin films were fabricated.•Hole mobility values measured by using conductive-Atomic Force Microscopy (c-AFM).•Carbo-mers as self-assembled hole transport monolayers in Organic Solar Cells (OSCs).