Designing Strategy for High Refractive Index Polymers: From the Molecular Level to Bulk Structure Control

High refractive index polymers (HRIPs) are essential materials for many optical applications, including organic light-emitting diodes (OLEDs), charge-coupled devices (CCDs), complementary metal oxide semiconductors (CMOS), eyeglasses, and optical waveguides. Various molecular designs, synthetic routes, and material preparation methods have been reported to increase the refractive index (RI) of polymers; however, increasing the RI using only organic (and classical) components is difficult. Other properties, such as low or high Abbe numbers (RI dispersion), low birefringence, and high transparency, are also required for HRIPs depending on the intended wavelength usage, which ranges from visible to infrared (IR) light and X-ray applications. This review summarizes the recent developments in HRIPs, including their synthesis, properties, and applications, and provides future prospects for achieving HRIPs with the desired performances.