A sandwich mixed (phthalocyaninato) (porphyrinato) europium triple-decker: Balanced-mobility, ambipolar organic thin-film transistor

A new sandwich mixed (phthalocyaninato) (porphyrinato) europium triple-decker (TPP)Eu2[Pc(OPh)8]2 (1), [TPP = dianion of 5,10,15,20-tetrakisporphyrin; Pc(OPh)8 = dianion of 2,3,9,10,16,17,23,24-octa(phenoxy)phthalocyanine], has been synthesized and characterized by a series of spectroscopic methods including MALDI-TOF mass spectrometry, 1H NMR spectroscopy, electronic absorption and infrared spectroscopy. The electrochemical property of 1 has been studied by cyclic voltammetry. Constructing the target triple-decker by coordination bonding between an europium ion and isoindole/tetrapyrrole nitrogen atoms from n-type double-decker (Eu[Pc(OPh)8]2) and p-type porphyrin (H2TPP) units, not only ensures the good solubility in conventional organic solvents, but more importantly successfully tunes the HOMO and LUMO levels into the range of ambipolar organic semiconductors required on the basis of electrochemical studies over 1. Using a solution-based quasi-Langmuir–Shäfer (QLS) method, the thin solid films of 1 were fabricated. The structure and properties of the thin films were investigated by UV–vis absorption spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Experimental results indicated the film crystallinity and general molecular order for (TPP)Eu2[Pc(OPh)8]2 molecules in the QLS films. Organic thin-film transistor (OTFT) fabricated from the QLS films of 1 was revealed to show ambipolar properties that have never been revealed for devices fabricated from a single-phthalocyanine/porphyrin mixed component using solution processable technique, with the highly balanced mobilities for holes and electrons of 0.04 cm2 V− 1 s− 1 and 0.08 cm2 V− 1 s− 1, respectively.