Highly stable deep red-to-NIR OLEDs with an external quantum efficiency of 4.9% from room temperature nanostructured columnar fluids based on hetero atom bay-annulated perylene bisimides

Abstract

A series of electron deficient perylene bisimides (PBIs) bearing 3,4,5-tridecylphenyl substituents on the imide N-atoms and bay-annulated with hetero atoms such as N, S, and Se in the bay positions of the perylene core via Cadogan reaction have been synthesized. These compounds were liquid crystalline at room temperature exhibiting a columnar hexagonal phase exclusively with the exception of S-annulated PBI, which exhibited a columnar oblique phase. These self-organizing organic semiconductors in one-dimensional (1D) columnar structures are unique by having better solubility, ease of purification, reproducibility, and ease of handling in comparison to polymers or single crystals. Detailed photophysical studies of these compounds show that they exhibit high molar extinction coefficients with wide absorption spectra covering most of the visible spectrum and bright red fluorescence, making them promising candidates for organic electronics. Further, they exhibited technologically important red electroluminescence. One of the solution-processed host–guest OLEDs (CBP as host at 1 wt% PBI-N¹⁰) exhibited a maximum EQE of 4.9%, lifetime of 12.4 h with an initial brightness of 2900 cd m⁻², and deep red/NIR emission. These results indicated that these materials exhibit significant potential in the field of columnar liquid crystal-based deep red/NIR emitters.