Steady-state photoconductivity of a supramolecular assembly of nonlinear optical molecules showing evidence of rectifier properties

The steady-state photoconductivity σ‖ along and σ⊥ perpendicular to aligned chains of nonlinear optical and other molecules included into parallel channels of perhydrotriphenylene (PHTP) inclusion compounds has been investigated. An anisotropy of σ‖/σ⊥ ∼102 supports an 1D-transport of charge carriers along (i) polar and (ii) non-polar chains of guest molecules. For (i) 4-iodo-4′-nitrobiphenyl (INBP) σ‖ is ∼4 (1)×10−14 S/cm, whereas a symmetrical guest, (ii) 4,4′-diiodobiphenyl (IIBP), shows a σ‖ of ∼2 (1)×10−13 S/cm. A significant asymmetry in the I(U)-curve for PHTP–INBP crystals is in agreement with the preferred direction of, e.g., electron transport along polar chains of INBP. This behaviour is typical for a molecular rectifier system, although the measured effect was small, presumably because of a relatively low electrical field strength applicable (E≤106 V/m) to macroscopically large crystals.