Naphthacene-doped and undoped 5,12-naphthacenequinone crystals: Preparation, crystal structures and optical characteristics
Introduction
In recent years, researches on organic semiconductor devices have developed rapidly. The high carrier mobility characteristics of organic crystals favor the study of the intrinsic charge transfer mechanism of organic semiconductor and the exploration of organic field-effect transistors (OFETs) with high performance.
Up to now, most of the molecular crystal devices are based on highly pure organic single crystals. However, doping, as an efficacious modulation to improve the performance of devices, has been widely applied in the field of organic semiconductors [1], [2], [3]. Maybe the similar effects could be achieved in crystal doping systems [4], [5], namely, organic mixed crystals. Moreover, the preparation of organic mixed crystals and the research of their properties are important for a deeper understanding of doped effect and energy transfer mechanism in organic semiconductors.
For organic mixed crystals, matched molecular structures are important for the growth of mixed crystals. And the overlap between the absorption spectrum of the acceptor and the emission spectrum of the donor is an essential precondition for the excitation energy transfer in organic mixed crystals.
In our work, we chose 5,12-naphthacenequinone (5,12-NpQ) as the target to investigate the intermolecular interaction mechanism of organic mixed crystals. 5,12-NpQ, as a kind of quinone compounds with small size, possesses peculiar photophysical and photochemical properties and might be used in biological systems, such as a good electron acceptor and so on [6], [7], [8]. However, researches on 5,12-NpQ crystals have not been reported ever before. In this paper, for the first time, we prepared 5,12-NpQ single crystal and high naphthacene (Np)-doped 5,12-NpQ crystal, a novel mixed crystal system, by crystallization from solution. Furthermore, the absorption, fluorescence spectra and transient photoluminescence (PL) decays of the above crystal systems have been investigated to probe into the optical characteristics of 5,12-NpQ with or without Np doping, which provided useful input for studying the interaction mechanism of the two components in organic mixed crystals [9], [10], [11], [12].
Section snippets
Preparation of 5,12-NpQ single and mixed crystals
5,12-NpQ single crystals were prepared from Np and hydrogen peroxide in carbon tetrachloride (CCl4) solution. After refluxing for 3 h, both heating and magnetic stirring were turned off and the solution was slowly cooled down to induce crystallization. Several hours later, needle-shaped 5,12-NpQ single crystals were observed in the solution, see Fig. 1(a).
Periodically, toothed structure was also observed on the surface of 5,12-NpQ single crystals. The average distance of periodicity is about
Crystal structures
In this work, 5,12-NpQ single crystals and 5,12-NpQ/Np mixed crystals were prepared for the first time by crystallization from solution. Table 1 gives the crystal data of the two systems, and Np single-crystal structure is also listed in Table 1 for comparison.
There are large differences between Np and 5,12-NpQ crystal structures because of the import of oxygen atoms, and their crystal systems are triclinic and orthorhombic, respectively. However, no obvious structural distinctions are found
Conclusions
5,12-NpQ single crystals and 5,12-NpQ/Np mixed crystals have been grown from solution. The foregoing results on their crystal structures show that the crystal doping does not lead to noticeable change of the crystal packing modes. It is supposed that the guest molecules appear at defects or vacancies of the crystal lattice, which does not distort the mixed crystal structure.
However, the doping effects on the optical properties of organic aromatic mixed crystals are significant. The fluorescence
Acknowledgments
This work was supported by the National Natural Science Foundation of China (Nos. 50325310, 50403001) and the National Research Fund for Fundamental Key 973 Projects (No. 2006CB806200). We are grateful to associate Prof. Y.G. Wei of the Tsinghua University for its assistance in crystal structure refinement and especially thank the support from Dr. Long Sheng Wang.
References (13)
- et al.
J. Crystal Growth
(2006) - et al.
Chem. Phys. Lett.
(1997) - et al.
Solid State Ionics
(1999) - et al.
Spectrochim. Acta Part A
(2002) - et al.
Mater. Res. Bull.
(2002) - R.M. Meixner, H. Goebel, F.A. Yildirim, et al. Appl. Phys. Lett. 2006 89 (9),...
Cited by (3)
Enrich mechanical, photo-acoustic, SHG and Z-scan studies on pure and crystal violet dye (CV) incorporated sodium acid phthalate crystal for optical applications
2019, Journal of Materials Science: Materials in ElectronicsEnhanced phosphorescence in dibenzophosphole chalcogenide mixed crystal
2011, CrystEngCommDoped organic crystals with high efficiency, color-tunable emission toward laser application
2009, Crystal Growth and Design