**3.1. Device fabrication**

We have fabricated multi-layered polymer CLC (PCLC) films for using them as wide-band reflectors or single-layered films for polarization-tunable OLEDs. As an experimental method for fabricating single-layered PCLC films is a part of fabricating multi-layered PCLC films, we introduce here only the fabrication of multi-layered films and skip the fabrication of single-layer films.

The fabrication process of multi-layered polymer PCLC films is shown in Fig. 20. Mixtures of two aromatic polyester liquid crystalline polymers (Nippon Oil Corporation; currently, JX Nippon Oil & Energy Corporation) are used to make PCLCs. One of the polymers (chiral polymer) contains 25% chiral units in its chemical composition and the other contains no chiral unit. By changing the ratio of the amounts of the two polymers, the helical pitch of PCLC (photonic band gap wavelength) is controlled.

**Figure 20.** Fabrication process of multi-layered PCLC films.

For fabricating three-layered PCLC films for use as a wide band reflector, the PCLC (λp=610 nm; chiral polymer 72 wt%) is spin-cast on glass substrates with unidirectionally rubbed polyimide (PI ; AL1256, JSR). Then, aqueous solution of polyvinyl alcohol (PVA) is spin-cast and the film surface is rubbed again unidirectionally. Another PCLC (λp= 510 nm; chrial polymer 87 wt%) is spin-cast on the rubbed PVA surface. The same procedure is repeated for preparing the third PCLC film (λp= 530 nm; chrial polymer 82 wt%). Finally PCLC films thus fabricated are cured for 30 min at 160 °C.

The fabrication method of a tunable phase retarder is as follows. The single-layered PCLC films are fabricated by spin coating the solution onto ITO glass substrates coated with PI rubbed unidirectionally at room temperature. The coated PCLC films are cured for 30 min at a temperature over 160 °C in a bake oven, and then quenched to room temperature. The sample cell is made of L-PCLC and PI coated glass substrates and is sustained by spacer. The NLC (ZLI2293, Merck) is introduced into an empty cell using capillary action. The illustration of the fabrication of the final cell is shown in Fig. 21

The OLED structure used here is fabricated in the same way as described in section 2.2. The vacuum evaporated OLEDs with structure of ITO/CuPc/TPD/Alq3/LiF/Al are described in section 3.2, an spin-coated OLEDs with structure of ITO/PEDOT:PSS/MEH-CN-PPV/LiF/Al are given in section 3.3.

**Figure 21.** Schematic illustration of tunable phase retarder. 63 Copyright 2008, American Institute of Physics.
