Sandwich cell geometry, surface

The first term is related to the bulk distortion energy, determined by the elastic deformation and external bulk field interactions. The second term is the surface contribution of the limiting surface D. The actual director field can be obtained by minimizing the energy. In a simple sandwich cell geometry (see Figure 4.27), the director (n(r)) can be expressed with the tilt angle as Q = cos (n k)> where k is the unit vector of the surface normal. 

The general structure of the bilayer solar cells is similar to the light-emitting diodes (LEDs). The devices are fabricated in sandwich geometry (Fig. 11.9). The active layer is sandwiched between two contacts an indium-tin-oxide electrode (ITO) (cathode) coated with a hole transport layer/glass or plastic foil. The blend polymer/PCBM solution was doctor-bladed on top of the hole conductor PEDOT PSS [poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid]. It improves the surface quality of ITO electrode. On the top of this polymer, about 100-nm aluminum layer is placed as an electrode (anode). 

In the geometry to be considered, the chiral nematic is contained between cell walls in the x, y plane with the uniform surface alignment layers designed to align the helix axis along x with the electric field applied along z (see Fig. 35). In such a sandwich like cell [29, 173-175], the director spirals along the x direction in the z, y plane and is therefore described by... 

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