title: Charge mobility and recombination in a new hole transporting polymer and its photovoltaic blend.
abstract: The charge mobility in a new hole transporting polymer, poly(2,6-bis(thiophene-2-yl)-3,5-dipentadecyldithieno[3,2-b;2',3'-d]thiophene) (PBTDTT-15), and its blend with (6,6)-phenyl-C(70)-butyric acid methyl ester (PC(70)BM) in a weight ratio of 1:3 at ambient atmosphere condition was investigated using time-of-flight (TOF) photoconductivity and photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) techniques. The bulk heterojunction based photovoltaic (PV) blend (PBTDTT-15:PC(70)BM (1:3)) exhibited a promising power conversion efficiency (PCE) of 3.23% under air mass 1.5 global (AM 1.5G) illumination of 100mW/cm(2). The charge mobility and recombination properties of the best performing cells were investigated. The hole mobility in the pure PBTDTT-15 was in the range of 4 x 10(-4) cm(2)/(V s), which was reduced almost 5 times in the PBTDTT-15:PC(70)BM (1:3) blend. The PhotoCELIV transient observed for the photovoltaic (PV) blend was dominated by electrons, with the charge mobility of the order of 10(-3) cm(2)/(V s), and a weak shoulder at a long time scale due to holes. The effective bimolecular recombination coefficient (beta) obtained for the PV blend deviated significantly from the Langevin recombination coefficient (beta(L)) indicating a phase-separated morphology. The obtained results indicate that the PBTDTT-15:PC(70)BM blend can be potential for organic solar cell applications.
authors.affiliation: Institute of Materials Research and Engineering, ASTAR (Agency for Science, Technology and Research), Singapore 117602.
authors.forename: Mein Jin
authors.initials: MJ
authors.lastname: Tan
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Goh
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Gaurav
authors.initials: G
authors.lastname: Pundir
authors.forename: Vijila
authors.initials: V
authors.lastname: Chellappan
authors.forename: Zhi-Kuan
authors.initials: ZK
authors.lastname: Chen
mesh_terms: D004574:Electromagnetic Fields; D008422:Materials Testing; D010777:Photochemistry / Q000379:methods*; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects*; D055672:Static Electricity
chemical_list: D011108:Polymers