title: Ultrafast Dynamics of Hole Injection and Recombination in Organometal Halide Perovskite Using Nickel Oxide as p-Type Contact Electrode.
abstract: There is a mounting effort to use nickel oxide (NiO) as p-type selective electrode for organometal halide perovskite-based solar cells. Recently, an overall power conversion efficiency using this hole acceptor has reached 18%. However, ultrafast spectroscopic investigations on the mechanism of charge injection as well as recombination dynamics have yet to be studied and understood. Using time-resolved terahertz spectroscopy, we show that hole transfer is complete on the subpicosecond time scale, driven by the favorable band alignment between the valence bands of perovskite and NiO nanoparticles (NiO(np)). Recombination time between holes injected into NiO(np) and mobile electrons in the perovskite material is shown to be hundreds of picoseconds to a few nanoseconds. Because of the low conductivity of NiO(np), holes are pinned at the interface, and it is electrons that determine the recombination rate. This recombination competes with charge collection and therefore must be minimized. Doping NiO to promote higher mobility of holes is desirable in order to prevent back recombination.
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Alice
authors.initials: A
authors.lastname: Corani
authors.affiliation: Department of Photonics, National Cheng Kung University , Tainan, Taiwan 701.
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Li
authors.affiliation: Department of Photonics, National Cheng Kung University , Tainan, Taiwan 701.
authors.forename: Po-Shen
authors.initials: PS
authors.lastname: Shen
authors.affiliation: Department of Photonics, National Cheng Kung University , Tainan, Taiwan 701.|Research Center for Energy Technology and Strategy (RCETS), Tainan, Taiwan 701.|Advanced Optoelectronic Technology Center (AOTC), Tainan, Taiwan 701.
authors.forename: Peter
authors.initials: P
authors.lastname: Chen
authors.affiliation: Department of Photonics, National Cheng Kung University , Tainan, Taiwan 701.|Research Center for Energy Technology and Strategy (RCETS), Tainan, Taiwan 701.|Advanced Optoelectronic Technology Center (AOTC), Tainan, Taiwan 701.
authors.forename: Tzung-Fang
authors.initials: TF
authors.lastname: Guo
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Amal
authors.initials: A
authors.lastname: El Nahhas
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Kaibo
authors.initials: K
authors.lastname: Zheng
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Arkady
authors.initials: A
authors.lastname: Yartsev
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Villy
authors.initials: V
authors.lastname: Sundström
authors.affiliation: Division of Chemical Physics, Lund University , Box 124, 221 00 Lund, Sweden.
authors.forename: Carlito S
authors.initials: CS
authors.lastname: Ponseca