Face-on Oriented Bilayer of Two Discotic Columnar Liquid Crystals for Organic Donor−Acceptor Heterojunction

Abstract

In this work, we report the achievement of a homeotropically (or face-on) oriented bilayer formed by a pair of discotic materials designed with specific properties: selective solubility, adjusted transition temperatures, and room temperature hexagonal columnar liquid-crystalline phase. The homeotropic orientation of the bilayer which is only a few hundred nanometers thick is performed by solution-processed deposition followed by thermal annealing in the geometry of open supported films and is evidenced by X-ray scattering. This represents the first proof of principle of an organic heterojunction based on two oriented columnar liquid crystal layers.

Discotic liquid crystals of transition metal complexes 48: Synthesis of novel phthalocyanine-fullerene dyads and effect of a methoxy group on their clearing points

“…They can greatly reduce their costs to manufacture the solar cells. Liquid crystalline D-A systems are braodly classified into three groups: smectic liquid crystals [1][2][3][4], liquid crystalline copolymers [5][6][7][8][9][10][11][12] and discotic columnar liquid crystals [13][14][15][16][17][18][19][20][21][22][23][24][25]. In 2004 Kim et al reported that an organic photovoltaic cell was fabricated by using liquid crystalline N,N'-diheptyl-3,4,9,10-perylenetetracarboxylicdiimide (PTCDI-C7) as the electron acceptor and zinc phthalocyanine (ZnPc) as the electron donor [1].…”

“…In comparison with smectic mesophases, discotic columnar mesophases are much easier to realize one-dimensional columnar structure perpendicular to both two electrodes (= homeotropic alignment) [14,23,25]. Columnar mesophases in homeotropic alignment are so favourable to obtain higher photoelectric conversion efficiency which can be attributable to larger - stacking of the -conjugated macrocycles [19].…”

“…The column can be a charge carrier path. In order to achieve efficient charge transfer, it is favourable to form perfect homeotropic alignment [14,19,23,25,29]. On the contrary, it is unfavourable to form both defects and polydomains in the homeotropic alignment [29].…”

“…On the contrary, it is unfavourable to form both defects and polydomains in the homeotropic alignment [29]. Up to date, there have been some donor-acceptor dyads showing columnar liquid crystalline mesophases [13][14][15][16][17][18][19][20][21][22][23][24][25]. For example, Bushby et al reported in 2005 that a triphenylene derivative connected with fullerene showed columnar mesomorphism [13].…”

Synthesis and thermotropic behavior of side chain polysiloxane bearing triphenylene moiety

“…In this organization, the molecules are face-on arranged on the surface with their columnar axis perpendicular to the substrate. This leads to the lack of birefringence in polarized light for typically a dendritic morphology of the LC phase [34][35][36]. We observed in TOA characteristic textures for this type arrangement [21] ( Figure 4 -image 5) indicating a strong interaction with the substrate (Figure&4b).…”