Analysis and simulation of the IV-characteristics of PPV-oligomer based Schottky diodes

Spin-coated organic blends of the five-ring PPV-type oligomer 2,5-di-n-octyloxy-1,4-bis((4 ' ,4 " -bisstyryl)styrylbenzene) (Ooct-OPV5) and polystyrene (PS) have been investigated in order to retrieve relevant parameters for the simulation of Schottky diodes of the type ITO/Ooct-OPV5:PS (1:1)/Al. A value of 0.53 eV for the Schottky-barrier formed at the Al/oligomer was determined by temperature-dependent IV-measurements. From the CV-characteristics of the same diode structures, an upper limit of 3.3 x 10(15) cm(-3) for the (p-type) doping concentration could be obtained. Thin film transistors have been fabricated to derive a value of 9 x 10(-5) cm(2)/V s for the mobility of the holes in a Ooct-OPV5:PS layer. The experimentally-determined parameters were used as input for numerical simulations. A good correspondence was found between the simulated and the experimental dark IV-curves of the ITO/Ooct-OPV5:PS (1:1)/Al device structure. For the illuminated IV-curves, a large difference between the experimental and simulated short-circuit photocurrent was observed due to incomplete dissociation of excitons. (C) 2001 Elsevier Science B.V. All rights reserved.