Three-layer organic solar cell with high-power conversion efficiency of 3.5%

To prepare organic solar cells with practical level of energy-conversion ef ficiency, the following strategies were adopted. By using HD as the photose nsitizer, which is heterodimer consisting of a weak electron-donating 5, 10 , 15, 20-tetra(2, 5-dimethoxyphenyl)porphyrinatozine and a weak electron-ac cepting 5, 10, 15-triphenyl-20-(3-pyridyl)porphyrin, intramolecular photoin duced electron transfer is promoted resulting in effective charge separatio n. To create an energetically well-arranged system, the HD was placed betwe en an electron-acceptor layer of PV (perylene-3, 4, 9, 10-tetracarboxyl-bis -benzimidazole) and strong electron-donor layer of MC (3-carboxymethyl-5- [ (3 -ethyl-2(3H)-benzothiazolylidine)ethylidene]-2thioxo-4-thiazolidinone), where photoinduced intermolecular electron transfer from HD to PV and rapid injection of electrons from MC to HD suppress back electron transfer in th e charge-separated HD. As a result of this, the three-layer solar cell Al/P V/HD/MC/Au showed fairly good photovoltaic properties, short-circuit photoc urrent quantum yield of 49.2%, open-circuit photovoltage of 0.39 V, hh fact or of 0.51, and energy conversion yield of 3.51% when irradiated with 445 n m monochromatic light of 12 mu W cm(-2) intensity transmitted through the A l/PV interface. Since the photocurrent hardly decreased with age, the photo current observed here is really from energy conversion and not from photoco rrosion of Al electrode being occasionally responsible for the photocurrent . (P) 2000 Elsevier Science B.V. All rights reserved.