Advanced structures of oxide TFT have been studied for various display applications. Oxide TFT with etch‐stopped layer has shown excellent uniformity and stability for display products. For mass production with low cost, however, back channel etched structure with/without titanium etch‐stopped one has been studied and demonstrated promising electrical properties comparable to etch stop structure. Furthermore, we have developed self‐aligned coplanar structure as one of ways to minimize parasitic capacitance and found excellent electrical properties and bias stability at 6 μm of channel length, which is demonstrated with 13.3 inch AMOLED.

We propose an optimal outcoupling structure of a quantum-dot light-emitting diode (QLED) and present material properties based on numerical calculations via the ray-tracing method, in which light extraction properties are obtained according to the surface wrinkles on a substrate. After analyzing the designed microstructure elements, the optimal model was derived and applied to the QLEDs; consequently, the outcoupling efficiency enhanced by 31%. The liquid crystalline polymer forming the random surface wrinkles not only achieves an excellent light extraction through plasma crosslinking but also facilitates large-area processes. We propose an optical design rule for high-efficiency QLED design by analyzing the electro-optical efficiency, emission spectrum, and angular radiation pattern of the optical device.

Liquid crystals (LCs) offer a promising playground for developing reconfigurable radio frequency devices due to their unique dielectric properties, including large birefringence and tunability. Previous research on reconfigurable phase shifters has primarily focused on studying loss, response, and tunability. However, the influence of surface-enforced alignment on LC remains an area that requires further exploration. Here, we designed a phase shifter using twisted nematic aligned cells. To characterize the phaseshifting behavior of the nematic LC, we employed the transmission line method within the frequency range of 5 to 8 GHz and extracted the dynamic electrical parameters. Numerical simulations based on finite element methods were conducted to predict the alignment of LC molecules and the propagation of waves within the test cell. The phase shifter achieved a phase difference of ∼220 • by applying a bias voltage to the LC. In particular, we compare the dynamic response of the phase shifter and a twisted LC configuration having a chiral dopant that responds 10 times faster than the homogeneous mode.INDEX TERMS Liquid crystal, dielectric anisotropy, phase shifter, twisted nematic configuration, chiral dopant.DOWON KIM (Member, IEEE) received the M.S. and Ph.D. degrees in electrical engineering from

The increasing prevalence of the Internet of Things (IoT) and the integration of digital technology into our daily lives have heightened security risks, necessitating more robust security measures. Physical unclonable functions (PUFs) have emerged as a promising solution, and PUFs offer a highly secure method to generate unpredictable and unique random digital values by leveraging inherent physical characteristics. However, traditional PUF implementations often involve complex hardware and circuitry, which can increase system costs and complexity. We propose an innovative approach utilizing a random wrinkles PUF (rw-PUF) based on a unique optical anisotropy and facile procedure. The rw-PUF consists of liquid crystal molecules with random orientations, resulting in a two-dimensional retardation map corresponding to a complex birefringence pattern. Moreover, our proposed technique allows for customization based on specific requirements using a spatial light modulator, enabling fast fabrication. One notable advantage of the rw-PUF is its ability to store multiple data sets within a single PUF without needing physical alterations. Additionally, we introduce the concept of "polyhedron authentication", which utilizes three-dimensional information storage in a voxelated rw-PUF. This approach demonstrates the feasibility of implementing high-level security technology by leveraging the unique properties of the rw-PUF.