Fractal Branched Microwires of Organic Semiconductor with Controlled Branching and Low-Threshold Amplified Spontaneous Emission

Fractals are quite normal in nature. However, fractal self-assembly of organic semiconductors remains challenging. Herein, we develop a facile solution assembly route to access organic microwires (MWs) comprising an oligo(p-phenyleneviny-lene) derivative (OPV-A) with and without branching. Instead of kinetically controlled beta-OPV-A microrods (MRs), thermodynami-cally favored alpha-OPV-A gives fractal branching MW patterns. As-prepared 9,10-dicyanoanthracene (DCA) alloyed assemblies function as seeds to allow for the heteroepitaxial growth of branching alpha-OPV-A MWs via either coassembly or two-step seeded growth. Consequently, fractal MWs with single-and multisite growth were both achieved, accompanied by tailorable branching densities and hierarchies. Thermodynamic control and a well-matched epitaxial relationship should be crucial to the formation of fractal MW patterns. Importantly, the aligned alpha-OPV-A MW array functions as a multichannel optical gain medium and exhibits low-threshold amplified spontaneous emission (ASE). The present work deepens the research into fractal self-assembly of functional organic semiconductors.

Automated summary

In this study, a facile solution assembly route is developed to achieve organic microwires (MWs) with fractal branching patterns. The thermodynamically favored alpha-OPV-A allows for the formation of fractal MWs with tailored branching densities and hierarchies. It is found that both coassembly and two-step seeded growth can be utilized to achieve single- and multisite growth of the branching alpha-OPV-A MWs. The aligned alpha-OPV-A MW array demonstrates multichannel optical gain medium properties and low-threshold amplified spontaneous emission (ASE).