Thin film deposition of organic hole transporting materials: optical, thermodynamic and morphological properties of naphthyl-substituted benzidines

• Type: Article in International Scientific Journal
• Date: 2018

Authors

José C. S. Costa (Author) FEUP; Adélio Mendes (Author) FEUP; Luís M. N. B. F. Santos (Author) Other

Journal

Title: Journal of Materials Science

Serial No. 18 Vol. 53

Pages: 12974-12987

ISSN: 0022-2461

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 7 Citations

ISI Web of Science

Scopus - 8 Citations

INSPEC

Associated Projects

LEPABE - Laboratório de Engenharia de Processos, Ambiente, Biotecnologia e Energia

LEPABE-2-ECO-INNOVATION - LEPABE-2-ECO-INNOVATION

Other information

Authenticus ID: P-00P-JDY

DOI: 10.1007/s10853-018-2547-2

Abstract (EN): Aromatic diamines and naphthyl-substituted benzidines (BDB, TPB, TPD, NPB, alpha-NPD, beta-NPB, TNB) are listed as one of the best series available of hole transport materials used as thin films in organic electronics (OLEDs, OPVs). High-quality, homogeneous and compact thin films (ae 300 nm of thickness) of this compound series were prepared by a physical vapor deposition procedure. SEM and XRD characterizations evidence the amorphous nature of the thin films of NPB, alpha-NPD, beta-NPB and TNB, prepared onto ITO and gold surfaces by a controlling mass flow rate. The semiconducting behavior of this class of pi-conjugated materials was investigated through UV-vis characterization by the determination of optical band gaps (ae 3 eV). According to DSC, SEM and XRD analyses, the materials evidenced an amorphous structure and high thermal stability in the glassy state. Analyzing the melting properties, the ratio T (g)/T (m) = 2/3 was observed for TPB and NPB, which have a higher molecular symmetry, while T (g)/T (m) = 3/4 was observed for the asymmetric beta-NPB and TPD. The first accurate measurements of the vapor pressures and thermodynamic properties of phase transition were obtained for the most common hole transport material (NPB) in OLEDs. The relative stability of the crystalline phases of the diamine derivatives (BDB, TPB, NPB) was found to be enthalpically driven, increasing linearly with the molar volume of the compound.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14