Newly synthesised gadolinium bis-phthalocyanine sandwich complex: ambipolar organic semiconductor

Time of flight photocurrent transient studies on 5 μm thick solution processed films of novel non-peripherally octa-octyl-substituted liquid crystalline gadolinium bis-1,4,8,11,15,18,22,25-octakis(octyl) phthalocyanines (8GdPc₂) provide a quantitative analysis of the intrinsic ambipolar charge transport relative to mesomorphic structure of this lanthanide compound. Characteristic liquid crystalline phases of these molecules have been identified from differential scanning calorimetry supported by observation from the UV–visible absorption, showing crystal-columnar mesophase and columnar mesophase-isotropic liquid transitions at 64.2 °C and 162 °C, respectively. The TOF carrier mobility is found to be structure dependent and highest values of 4.73 × 10⁻⁶ m² V⁻¹ s⁻¹ and 1.6 × 10⁻⁶ m² V⁻¹ s⁻¹ have been estimated for hole and electron mobilities for hexagonally packed, columnar structures of the spin-coated films. These results are exploitable for development of single molecule based all organic complimentary analogue and digital circuits with tunable field effect performance. (paper)