title: Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells.
abstract: Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I(-), and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Pathak
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Nobuya
authors.initials: N
authors.lastname: Sakai
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Stergiopoulos
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Pabitra K
authors.initials: PK
authors.lastname: Nayak
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Nakita K
authors.initials: NK
authors.lastname: Noel
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Amir A
authors.initials: AA
authors.lastname: Haghighirad
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.|Mathematical Institute, University of Oxford, Woodstock Road, Oxford OX2 6GG, UK.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Burlakov
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: Dane W
authors.initials: DW
authors.lastname: deQuilettes
authors.affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Aditya
authors.initials: A
authors.lastname: Sadhanala
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing 100084, China.
authors.forename: Wenzhe
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing 100084, China.
authors.forename: Liduo
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Ginger
authors.affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford, Parks road, Oxford OX1 3PU, UK.
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith