Observation of Strong J-Aggregate Light Emission in Monolayer Molecular Crystal on Hexagonal Boron Nitride
Beilei Sun1, Xin Xu1, Guodong Zhou1
1Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P. R. China.
Abstract:
J-aggregates are widely used in studies of light-matter interaction and organic optoelectronic devices. Although J-aggregate films can be fabricated on salt by epitaxial growth method, the size is limited to hundreds of nanometer. In this work, with hexagonal boron nitride (h-BN) as a substrate, highly crystalline J-aggregate ultrathin films of N,N'-ditridecylperylene 3,4,9,10-tetracarboxylic diimide (PTCDI-C13) are achieved by physical vapor transport (PVT) method. Significant bathochromically shifted absorption band and narrowed 0-0 transition are observed in the monolayer PTCDI-C13 crystal on h-BN. The exciton coherence number Ncoh of monolayer J-aggregate film extracted from the photoluminescence (PL) spectrum is up to 15 at T = 140 K, which is higher than that of the epitaxially grown layer on salt. Beyond the first molecular layer, the multilayer crystal on h-BN is dominated by H-aggregates. Further study shows that that the first molecular layer on h-BN adopts the highly ordered face-on configuration, while the overlayers adopt the edge-on motif. As a comparison, only H-aggregate PTCDI-C13 ultrathin films are found on SiO2 substrates, but no J-aggregates. The results suggest that high-quality J-aggregates can be prepared by utilizing appropriate substrates via physical vapor transport.
Related Concept Videos
02:18X-ray Crystallography
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:18Network Covalent Solids
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
02:54Molecular and Ionic Solids
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
04:01VSEPR Theory and the Effect of Lone Pairs