Combination of Photoinduced Alignment and Self-Assembly to Realize Polarized Emission from Ordered Semiconductor Nanorods

One-dimensional semiconductor nanorods are a very promising class of materials for applications in modern optoelectronic devices, such as light-emitting diodes, solar cells, displays, and lasers. Their ability to emit linearly polarized light is considered to simplify device structures and improve the overall efficiencies. To ensure macroscopic polarization in such devices, the biggest challenge is the long-range alignment of nanorods by controllable means. We propose a technique that combines photoinduced alignment with nanorod's self-assembly. With this approach, we are able to actively control the alignment directions of highly emissive semiconductor nanorods in both microscopic and macroscopic scale with the order parameter as high as 0.87. As a result, polarized emission has been achieved with the degree of polarization of 0.62. Furthermore, patterned alignment of nanorods with spatially varying local orientations has been realized to demonstrate the great flexibility of this approach. Besides opportunities for applications, our method of alignment offers insights into host-guest interactions governing self-assembly of colloidal nanocrystals within the host molecular matrix.