Controllable Molecular Packing Motif and Overlap Type in Organic Nanomaterials for Advanced Optical Properties

Abstract

The optical properties of organic materials are very sensitive to subtle structural modification, and a proper understanding of the structure-property relationship is essential to improve the performance of organic electronic devices. The phase transitions of the η-CuPc to the α-CuPc, then to the β-CuPc were investigated using In situ X-ray diffraction and the differential scanning calorimetry (DSC). The five stages in the phase-transition process from low to high-temperature were observed, which consisted of (1) the η-CuPc; (2) a mixture of the η- and α-CuPc; (3) a mixture of the η-, α- and β-CuPc; (4) a mixture of the α- and β-CuPc; and (5) the β-CuPc. The vibrational and optical properties at different phase-transition stages were correlated to molecular packing motif and molecule overlap type through systematic analyses of the Fourier–transform infrared, Raman and UV-VIS spectra. Moreover, the mechanism for the morphology evolution was also discussed in detail.

Keywords

• nanomaterials
• copper phthalocyanine
• crystal structure
• phase transition
• optical properties
• vibrational properties