Novel Photoalignment Method Based on Low-Molecular-Weight Azobenzene Dyes and Its Application for High-Dichroic-Ratio Polarizers

Abstract

Photoalignment is a simple technique for the manipulation of molecular orientations, which has been widely used in liquid crystal displays. Here, we propose a novel photoalignment method, in which an azobenzene dye thin film is deposited by thermal evaporation and in situ exposed to linearly polarized light simultaneously. We obtain polarizers with a dichroic ratio of up to 62, which is the highest value ever realized by a photoalignment method. Moreover, the polarizing thin film has a thickness of just 200 nm, compatible with flexible substrates, making it perfect for use as a dichroic polarizer in ultrathin and flexible displays.

Strong Linearly Polarized Photoluminescence and Electroluminescence from Halide Perovskite/Azobenzene Dye Composite Film for Display Applications

“…Upon exposure to the blue polarized irradiation (405 nm, 30 mW cm −2 ), the AD1 molecules absorb the light. The absorption of the molecules is proportional to cos 2 α, where α is the angle between the absorption oscillator of the AD1 molecules and the polarization of the pump light . The molecules located at the smaller α are more able to be excited and rotate via iterative cis‐trans isomerization and diffusion until the absorption oscillator is perpendicular to the pump light polarization direction.…”

“…Poly( N ‐vinyl carbazole) (PVK) was purchased from Luminescence Technology Corp. 5‐aminovaleric acid bromide (AVAB), phenethylammonium bromide (PEAB) and iso‐propylammonium bromide (IPAB) were purchased from Great Cell Solar. ZnO nanoparticles were purchased from Poly Optoelectronics, the AD1 used in this work was synthesized and purified following reported works, the SD1 used in this work was synthesized following reported work…”

Photoinduced Reorientation and Photofunctional Control of Liquid Crystalline Copolymers with in Situ-Formed N-Benzylideneaniline Derivative Side Groups

“…Introducing a functionality into the reoriented film upon or after the photoinduced reorientation should expand the applicability of molecularly oriented structures. Many studies have focused on the alignment of functional materials on the thin photoalignment layer to fabricate birefringent and optical functional films. − Oriented films with photo and optical functionalities have been prepared through cooperative reorientation of the functional groups in photoalignable films. − In these cases, photoalignable moieties for the molecular orientation remain in the oriented films, which may affect the optical property and durability of the film. Hence, eliminating the photoalignable moieties in the oriented film and simultaneously introducing photofunctional moieties will directly change the optical and thermal properties of photoaligned films.…”

Fabrication and optical properties of dichroic polarizing films based on poly(vinyl alcohol)-heteropolyacid nanocomposites

“…Thin dichroic polarizing films can be fabricated by direct alignment of dichroic liquid crystalline dye molecules on solid substrates. A great deal of research has been performed on these systems in the recent years, and rather high values of polarization efficiency (degree of polarization) have been achieved using several different methods of film preparation [11][12][13]. However, the reported high polarization characteristics of the films cover only a narrow wavelength range of about 450-550 nm.…”