title: Ultrathin ammonium heptamolybdate films as efficient room-temperature hole transport layers for organic solar cells.
abstract: Ammonium heptamolybdate (NH4)6Mo7O24·4H2O (AHM) and its peroxo derivatives are analyzed as solution-processed room temperature hole transport layer (HTL) in organic solar cells. Such AHM based HTLs are investigated in devices with three different types of active layers, i.e., solution-processed poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester(P3HT/PC60BM), poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]/[6,6]-phenyl C70-butyric acid methyl ester(PCDTBT/PC70BM) and evaporated small molecule chloro(subphthalocyaninato)boron(III) (SubPc)/C60. By virtue of their high work functions, AHM based HTLs outperform the commonly used poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) HTL for devices employing deep HOMO level active materials. Moreover, devices using AHM based HTLs can achieve higher short circuit current (Jsc) than the ones with evaporated molybdenum oxide(eMoO3), and thus better power conversion efficiency (PCE). In addition, P3HT/PC60BM devices with AHM based HTLs show air stability comparable to those with eMoO3, and much better than the ones with PEDOT:PSS.
authors.affiliation: Imec , Kapeldreef 75, 3001 Heverlee, Belgium.
authors.forename: Weiming
authors.initials: W
authors.lastname: Qiu
authors.forename: Afshin
authors.initials: A
authors.lastname: Hadipour
authors.forename: Robert
authors.initials: R
authors.lastname: Müller
authors.forename: Bert
authors.initials: B
authors.lastname: Conings
authors.forename: Hans-Gerd
authors.initials: HG
authors.lastname: Boyen
authors.forename: Paul
authors.initials: P
authors.lastname: Heremans
authors.forename: Ludo
authors.initials: L
authors.lastname: Froyen
keywords: H2O2 modification; ammonium heptamolybdate; hole transport layers; organic solar cells; room temperature