title: UV-Induced Oxygen Removal for Photostable, High-Efficiency PTB7-Th:PC71BM Photovoltaic Cells.
abstract: Solution-processed ZnO sol-gel or nanoparticles are widely used as the electron-transporting layer (ETL) in optoelectronic devices. However, chemisorbed oxygen on the ZnO layer surface has been shown to be detrimental for the device performance as well as stability. Herein, we demonstrate that chemisorbed oxygen removal based on UV illumination of the ZnO surface layer under a nitrogen atmosphere can, simultaneously, improve the power conversion efficiency and photostability of PTB7-Th:PC71BM-based inverted polymer solar cells. By a systematic study of such a UV illumination procedure, we obtained optimal conditions where both the cell efficiency and stability were improved. We fabricated cells with a power conversion efficiency higher than 9.8% and with a T80lifetime longer than 500 h, corresponding to about a 2.5-fold enhancement relative to non-UV-treated ZnO reference devices.
authors.affiliation: ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels (Barcelona), Spain.
authors.forename: Quan
authors.initials: Q
authors.lastname: Liu
authors.affiliation: ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels (Barcelona), Spain.
authors.forename: Paola
authors.initials: P
authors.lastname: Mantilla-Perez
authors.affiliation: ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels (Barcelona), Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Montes Bajo
authors.affiliation: ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels (Barcelona), Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Romero-Gomez
authors.affiliation: ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology , 08860 Castelldefels (Barcelona), Spain.|Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya , 08222 Terrassa, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Martorell
keywords: PTB7-Th; molecular oxygen; photostability; polymer solar cells; sol−gel ZnO