Pure red emitting elastic organic single crystals as flexible optical waveguides and circuits

Abstract

The crystal engineering approach has been advanced to precisely tune organic crystals' mechanical and optical properties and expand their potential as prospective materials in optoelectronic devices. However, the bottleneck for full-color emissive devices is that they require pure-color emissive materials. Herein, we achieved the design of a flexible single crystal of N-(3-bromo-5-chlorosalicylidene)-1-aminopyrene (ACBS), which not only exhibits excellent elastic flexibility but also shows the rare property of pure red emission with the standard Commission Internationale de l’Eclairage (CIE) coordinates of (0.67, 0.33). The single crystal structure revealed characteristic herringbone chains, which impart them with remarkable elasticity. Notably, realizing their unique standard red emissions, we show the first example of a flexible organic optical waveguide comprising a pyrene unit. The crystals were shown to be capable of propagating their fluorescence effectively, thus exhibiting potential as an active waveguide. A reconfigurable 2 × 2 directional coupler (DC) was also designed to demonstrate circuits for integrated photonic devices. This study broadens the scope for achieving all-organic flexible crystalline materials with saturated red emissions for flexible photonic, optoelectronic, and full-color devices.