title: Enhanced photoluminescence and solar cell performance via Lewis base passivation of organic-inorganic lead halide perovskites.
abstract: Organic-inorganic metal halide perovskites have recently emerged as a top contender to be used as an absorber material in highly efficient, low-cost photovoltaic devices. Solution-processed semiconductors tend to have a high density of defect states and exhibit a large degree of electronic disorder. Perovskites appear to go against this trend, and despite relatively little knowledge of the impact of electronic defects, certified solar-to-electrical power conversion efficiencies of up to 17.9% have been achieved. Here, through treatment of the crystal surfaces with the Lewis bases thiophene and pyridine, we demonstrate significantly reduced nonradiative electron-hole recombination within the CH(3)NH(3)PbI(3-x)Cl(x) perovskite, achieving photoluminescence lifetimes which are enhanced by nearly an order of magnitude, up to 2 μs. We propose that this is due to the electronic passivation of under-coordinated Pb atoms within the crystal. Through this method of Lewis base passivation, we achieve power conversion efficiencies for solution-processed planar heterojunction solar cells enhanced from 13% for the untreated solar cells to 15.3% and 16.5% for the thiophene and pyridine-treated solar cells, respectively.
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Nakita K
authors.initials: NK
authors.lastname: Noel
authors.forename: Antonio
authors.initials: A
authors.lastname: Abate
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Stranks
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Parrott
authors.forename: Victor M
authors.initials: VM
authors.lastname: Burlakov
authors.forename: Alain
authors.initials: A
authors.lastname: Goriely
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
keywords: coordinate bonding; defect sites; organic−inorganic perovskite; perovskite solar cells; photoluminescence; surface passivation; under-coordinated atoms