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

To prepare organic solar cells with practical level of energy-conversion efficiency, the following strategies were adopted. By using HD as the photosensitizer, which is heterodimer consisting of a weak electron-donating 5, 10, 15, 20-tetra(2, 5-dimethoxyphenyl)porphyrinatozine and a weak electron-accepting 5, 10, 15-triphenyl-20-(3-pyridyl)porphyrin, intramolecular photoinduced electron transfer is promoted resulting in effective charge separation. To create an energetically well-arranged system, the HD was placed between 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 the charge-separated HD. As a result of this, the three-layer solar cell Al/PV/HD/MC/Au showed fairly good photovoltaic properties, short-circuit photocurrent quantum yield of 49.2%, open-circuit photovoltage of 0.39 V, hh factor of 0.51, and energy conversion yield of 3.51% when irradiated with 445 nm monochromatic light of 12 mu W cm(-2) intensity transmitted through the Al/PV interface. Since the photocurrent hardly decreased with age, the photocurrent observed here is really from energy conversion and not from photocorrosion of Al electrode being occasionally responsible for the photocurrent. (P) 2000 Elsevier Science B.V. All rights reserved.