Self-Assembly of Patchy Colloidal Rods into Photonic Crystals Robust to Stacking Faults

Area of Science:

• Materials Science
• Nanotechnology
• Computational Physics

Background:

• Diamond-structured colloidal photonic crystals are crucial for visible light management due to their complete photonic band gap (PBG).
• Achieving these structures via self-assembly is challenging, hindered by building block design, sensitivity to stacking faults, and achieving a practical refractive index.

Purpose of the Study:

• To computationally address the challenges in realizing diamond-structured photonic crystals through self-assembly.
• To design building blocks and self-assembly routes that yield structures with a complete photonic band gap (PBG).

Main Methods:

• Utilized reverse engineering to define design principles for the rod-connected diamond (RCD) structure.
• Devised two self-assembly routes using designer triblock patchy colloidal rods, proceeding via tetrahedral clusters.
• Employed Monte Carlo simulations to analyze self-assembly pathways and the resulting photonic band gap (PBG) properties.

Main Results:

• Identified design principles for the RCD structure and developed two self-assembly routes yielding mixed cubic and hexagonal polymorphs.
• Demonstrated that these routes avoid a metastable amorphous phase, leading to structures related to RCD.
• Showed that both polymorphs and their randomly stacked hybrids support spectrally overlapping complete photonic band gaps (PBGs).

Conclusions:

• The computational approach successfully addresses key challenges in fabricating diamond-structured photonic crystals.
• The developed self-assembly routes offer a scalable method for producing photonic crystals with tunable PBGs.
• Random stacking of polymorphs circumvents the need for precise structural selection, facilitating large-scale fabrication.