title: Significant Stability Enhancement in High-Efficiency Polymer:Fullerene Bulk Heterojunction Solar Cells by Blocking Ultraviolet Photons from Solar Light.
abstract: Achievement of extremely high stability for inverted-type polymer:fullerene solar cells is reported, which have bulk heterojunction (BHJ) layers consisting of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by employing UV-cut filter (UCF) that is mounted on the front of glass substrates. The UCF can block most of UV photons below 403 nm at the expense of ≈20% reduction in the total intensity of solar light. Results show that the PTB7-Th:PC71BM solar cell with UCF exhibits extremely slow decay in power conversion efficiency (PCE) but a rapidly decayed PCE is measured for the device without UCF. The poor device stability without UCF is ascribed to the oxidative degradation of constituent materials in the BHJ layers, which give rise to the formation of PC71BM aggregates, as measured with high resolution and scanning transmission electron microscopy and X-ray photoelectron spectroscopy. The device stability cannot be improved by simply inserting poly(ethylene imine) (PEI) interfacial layer without UCF, whereas the lifetime of the PEI-inserted PTB7-Th:PC71BM solar cells is significantly enhanced when UCF is attached.
authors: Organic Nanoelectronics Laboratory School of Applied Chemical Engineering Kyungpook National University Daegu 702-701 Republic of Korea.
authors: Jaehoon
authors: J
authors: Jeong
authors: Organic Nanoelectronics Laboratory School of Applied Chemical Engineering Kyungpook National University Daegu 702-701 Republic of Korea.
authors: Jooyeok
authors: J
authors: Seo
authors: Center for Plastic Electronics Department of Physics Blackett Laboratory Imperial College London London SW7 2AZ UK.
authors: Sungho
authors: S
authors: Nam
authors: Organic Nanoelectronics Laboratory School of Applied Chemical Engineering Kyungpook National University Daegu 702-701 Republic of Korea.
authors: Hyemi
authors: H
authors: Han
authors: Organic Nanoelectronics Laboratory School of Applied Chemical Engineering Kyungpook National University Daegu 702-701 Republic of Korea; Priority Research Center Research Institute of Advanced Energy Technology Kyungpook National University Daegu 702-701 Republic of Korea.
authors: Hwajeong
authors: H
authors: Kim
authors: Center for Plastic Electronics Department of Physics Blackett Laboratory Imperial College London London SW7 2AZ UK.
authors: Thomas D
authors: TD
authors: Anthopoulos
authors: Center for Plastic Electronics Department of Physics Blackett Laboratory Imperial College London London SW7 2AZ UK; Division of Mathematical, Physical and Life Sciences University of Oxford Oxford OX1 3PD UK.
authors: Donal D C
authors: DD
authors: Bradley
authors: Organic Nanoelectronics Laboratory School of Applied Chemical Engineering Kyungpook National University Daegu 702-701 Republic of Korea.
authors: Youngkyoo
authors: Y
authors: Kim
keywords: UV light; degradation; morphology; polymer:fullerene solar cells; stability