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

The steady-state photoconductivity sigma(parallel to) along and sigma(perpe ndicular to) perpendicular to aligned chains of nonlinear optical and other molecules included into parallel channels of perhydrotriphenylene (PHTP) i nclusion compounds has been investigated. An anisotropy of sigma(parallel t o)/sigma(perpendicular to) similar to 10(2) supports an 1D-transport of cha rge carriers along (i) polar and (ii) non-polar chains of guest molecules. For (i) 4-iodo-4'-nitro-biphenyl (INBP) sigma(parallel to) is similar to 4 (1) x 10(-14) S/cm, whereas a symmetrical guest, (ii) 4,4'-diiodobiphenyl ( IIBP), shows a sigma(parallel to) of similar to 2 (1) x 10(-13) S/cm. A sig nificant asymmetry in the I(U)-curve for PHTP-INBP crystals is in agreement with the preferred direction of, e.g., electron transport along polar chai ns of INBP. This behaviour is typical for a molecular rectifier system, alt hough the measured effect was small, presumably because of a relatively low electrical field strength applicable (E less than or equal to 10(6) V/m) t o macroscopically large crystals. (C) 1999 Elsevier Science S.A. All rights reserved.