title: High-Performance Inverted Organic Photovoltaics Without Hole-Selective Contact.
abstract: A detailed investigation of the functionality of inverted organic photovoltaics (OPVs) using bare Ag contacts as the top electrode is presented. The inverted OPVs without a hole-transporting layer (HTL) exhibit a significant gain in hole-carrier selectivity and power-conversion efficiency (PCE) after exposure in ambient conditions. Inverted OPVs comprised of ITO-ZnO-poly(3-hexylthiophene-2,5-diyl)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM)-Ag demonstrate over 3.5% power conversion efficiency only if the devices are exposed in air for over 4 days. As concluded through a series of measurements, the oxygen presence is essential to obtaining fully operational solar cell devices without HTL. Moreover, accelerated stability tests under damp heat conditions (RH = 85% and T = 65 °C) performed to nonencapsulated OPVs demonstrate that HTL-free inverted OPVs exhibit comparable stability to the reference inverted OPVs. Importantly, it is shown that bare Ag top electrodes can be efficiently used in inverted OPVs using various high-performance polymer-fullerene bulk heterojunction material systems demonstrating 6.5% power-conversion efficiencies.
authors.affiliation: Molecular Electronics and Photonics Research Unit, Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology , Limassol, 3603, Cyprus.
authors.forename: Achilleas
authors.initials: A
authors.lastname: Savva
authors.affiliation: Molecular Electronics and Photonics Research Unit, Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology , Limassol, 3603, Cyprus.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Burgués-Ceballos
authors.affiliation: Molecular Electronics and Photonics Research Unit, Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology , Limassol, 3603, Cyprus.
authors.forename: Giannis
authors.initials: G
authors.lastname: Papazoglou
authors.affiliation: Molecular Electronics and Photonics Research Unit, Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology , Limassol, 3603, Cyprus.
authors.forename: Stelios A
authors.initials: SA
authors.lastname: Choulis
keywords: bare silver electrodes; carrier-selective contacts; electrodes; hole selectivity; hole-transport-layer-free OPVs; inverted organic photovoltaics; photocurrent mapping