Makromol. Chem. zyxwvut 194,2985 zyxwvut -2999 (1993) zyxwvu 2985 zy Conductivity and photoconductivity of undoped and doped Langmuir-Blodgett films of a polymer with hexaalkoxytri- phenylene side-groups Christian Catry, Mark Van der Auweraer: Frans C De Schryver Chemistry Department K. U. Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium Holger Bengs, Lucas Haussling, Olaf Karthaus, Helmut Ringsdorf Institut fur Organische Chemie, Johannes Gutenberg Universitat Mainz J. J. Becher-Weg 18-20, 55128 Mainz, Germany Received: September 17, 1992; Revised manuscript of March 22, 1993) SUMMARY Langmuir-Blodgett films from a polymer with triphenylene moieties in the side groups deposited on a quartz substratum with aluminium and gold electrodes show a dark conductivity in the plane of the Langmuir-Blodgett film. This dark conductivity is increased using gold electrodes as compared with aluminium electrodes. It depends in a superlinear way upon the applied electric field and is not enhanced by oxygen. The dark conductivity can be enhanced by doping the Langmuir-Blodgett films with iodine but it is not influenced by doping the Langmuir- Blodgett films with 2,4,7-trinitro-9-fluorenone. Upon excitation in the absorption band of the triphenylene moiety an in-plane photocurrent, which is enhanced by oxygen, could be observed. Also the photocurrent is enhanced by using gold electrodes. Doping the Langmuir-Blodgett films with iodine or zyxwvut 2,4,7-trinitro-9-fluorenone quenches the photocurrent. Up to 10 W/m’ the photocurrent depends linearly upon the intensity of the incident light. Introduction The conductivity of the bulk phases of undoped and doped hexaalkoxytriphenylenes was linked to their molecular organization I*’). The stacked arrangement and the small intermolecular distance are expected to induce high charge mobility 3-9). Because a stacked molecular organization, leading to high conductivity or photoconductivity, can also be obtained in Langmuir-Blodgett films zyxw ‘O-”), it is of interest to investigate the conductive and photoconductive properties of the Langmuir-Blodgett films of hexaalkoxytriphenylenes. Beside their tendency to adapt a stacked organization in crystalline phases or discotic me so phase^^^-^^) or mono layer^'^-^') those compounds are characterized by a low oxidation potential 32) which would favour injection of charge carriers from an electrode by a thermal p r o c e ~ s ~ ~ - ~ ~ ) or by the dissociation of an ex~iton~~-~~). It is also expected that addition of suitable electron acceptorsa) will lead to an increase of the low equilibrium density4’) of charge carriers by several orders of magnitude ‘9 2,42-44). Because the symmetric hexaalkoxytriphenylenes cannot be transferred to stable condensed Langmuir-Blodgett the model compound 1 26,28, 29) (5-[3-(5- hydroxypentyloxy)-6,7,10,11 -tetrakis(pentyloxy)triphenylen-2-yloxy]pentanol) and polymer 2 containing 10-[3,6,7,10,1 I-pentakis(pentyloxy)triphenylen-2-yloxy]decyl zy 0 1993, Hiithig zyxwvuts & Wepf Verlag, Basel CCC 0025-116)</93/$05.00