Pentacene based photovoltaic devices

Photovoltaic diodes based on iodine- and bromine-doped pentacene single cry stals as well as thin films (TFs) have been prepared. Two different device structures, a Schottky diode with a Mg/Al back contact and a heterojunction with a ZnO:Al window layer, are investigated. An immense increase of the p hotovoltaic conversion efficiency of these devices is observed upon doping with iodine as well as bromine, which is ascribed to a reduction of the ser ies resistance, an increase in quantum efficiency, and a red shift of the a bsorption spectrum. AM1.5 efficiencies of 2.7 and 4.5% are obtained for sin gle crystal Schottky diodes and heterojunctions, respectively. In addition, efficiencies exceeding 2% are realized in TF devices on flexible plastic s ubstrates. (C) 2001 Elsevier Science B.V. All rights reserved.