FORMATION OF ALIGNED PERIODIC PATTERNS DURING THE CRYSTALLIZATION OF ORGANIC SEMICONDUCTOR THIN FILMS

Self-organizing patterns with micrometer-scale feature sizes are promising for the large area fabrication of photonic devices and scattering layers in optoelectronics. Pattern formation would ideally occur in the active semiconductor to avoid the need for further processing steps. The present disclosure includes approaches to form period patterns in single layers of organic semiconductors by an annealing process. When heated, a crystallization front propagates across the film, producing a sinusoidal surface structure with wavelengths comparable to that of near-infrared light. These surface features form initially in the amorphous region within a micron of the crystal growth front, likely due to competition between crystal growth and surface mass transport. The pattern wavelength can be tuned by varying film thickness and annealing temperature, millimeter scale domain sizes are obtained. Aspects of the disclosure can be exploited for self-assembly of microstructured organic optoelectronic devices, for example.