Ligand Shell Engineering to Achieve Optimal Photoalignment of Semiconductor Quantum Rods for Liquid Crystal Displays

• Published in: Advanced functional materials Vol. 29; no. 3
• Main Authors: Zhang, Wanlong, Prodanov, Maksym F., Schneider, Julian, Gupta, Swadesh K., Dudka, Tetiana, Vashchenko, Valerii V., Rogach, Andrey L., Srivastava, Abhishek K.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 17.01.2019
• Subjects: Cadmium selenides; Compatibility; enhancement films; Flat panel displays; LCDs; ligand design; Ligands; Liquid crystal displays; Materials science; Optical properties; photoalignment; quantum rods; Rods
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201805094

The photoalignment process to align semiconductor quantum rods (QRs) in the liquid crystal monomer (LCM) matrix is a flexible technology; however, the optical quality of the resulting enhancement films drops at high concentrations of the QRs. The compatibility between the ligand shell on the QRs and the LCM plays an important role in avoiding this issue. Herein, several kinds of ligand shells on the rod‐in‐rod CdSe/CdS QRs are designed, without affecting the optical properties of QRs, and their compatibility with LCM molecules is studied. Promesogenic dendritic ligands in combination with relatively short alkylphosphonic acids are found to provide the highest optical quality, without QR aggregation, and so the high brightness of the resulting enhancement films, even at higher concentrations of QRs in LCM, which is perfectly suitable for the application in liquid crystal displays. The photoalignment process, to align quantum rods (QRs) in the liquid crystal monomer (LCM) matrix, is an advanced technology for QRs alignment, but the compatibility between ligands, on QRs, and LCM is critically important. After studying several alternatives, the combination of dendritic and hexylphosphonic acid ligands was found to be highly compatible with LCM and provides good alignment for QRs.