The direct emission of circularly polarized (CP) light improves the efficiency of an organic light-emitting diode and characterizes the secondary structure of proteins. In most cases, CP light is generated from a luminescent layer containing chiral characteristics, thereby generating only one kind of CP light in an entire device. Here, we propose direct CP light emissions using a twisted achiral conjugate polymer without any chiral dopant as an emitting layer (EML). The twisted structure is induced in the mesogenic conjugate polymer due to its elasticity by applying different alignment directions to its upper and lower interfaces. Furthermore, we demonstrate the simultaneous emission of orthogonal CP light in a single luminescent device by patterning different alignment directions on the surfaces of the EML. The light source with multipolarization including the orthogonal CP states is applicable to many applications in biosensors and optical devices.

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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 successfully realized world first 77-inch transparent flexible OLED display with Ultra High Definition (UHD) resolution, which can be rolled up to a radius of 80 mm with a transmittance of 40%. The process flow and key technologies to fabricate a large size transparent flexible OLED panel will be discussed.

Copper(I) oxide (Cu 2 O), which is obtained from copper(II) oxide (CuO) through a reduction process, is a p-type oxide material with a band gap of 2.1−2.4 eV. However, the switching performance of typical Cu 2 O thin-film transistors (TFTs) is poor because the reduction process increases the concentration of oxygen vacancies (V O ), which interfere with the conduction of hole carriers. Ga with high oxygen affinity was doped in Cu 2 O thin films to decrease V O during the reduction process. As a result, the V O concentration of 1.56 at % for Ga-doped Cu 2 O (Ga:Cu 2 O) thin films decreased from 20.2 to 7.5% compared to pristine Cu 2 O thin films. Accordingly, the subthreshold swing or S-factor, on/off-current ratio (I on/off ), saturation mobility (μ sat ), and threshold voltage (V th ) of Ga:Cu 2 O TFTs were improved compared to pristine Cu 2 O TFTs with values of 7.72 from 12.50 V/dec, 1.22 × 10 4 from 2.74 × 10 2 , 0.74 from 0.46 cm 2 /Vs, and −4.56 from −8.06 V, respectively. These results indicate that Ga plays an important role in improving the switching performance of p-type Cu 2 O TFT.