title: Probing the energy levels of perovskite solar cells via Kelvin probe and UV ambient pressure photoemission spectroscopy.
abstract: The field of organo-lead halide perovskite solar cells has been rapidly growing since their discovery in 2009. State of the art devices are now achieving efficiencies comparable to much older technologies like silicon, while utilising simple manufacturing processes and starting materials. A key parameter to consider when optimising solar cell devices or when designing new materials is the position and effects of the energy levels in the materials. We present here a comprehensive study of the energy levels present in a common structure of perovskite solar cell using an advanced macroscopic Kelvin probe and UV air photoemission setup. By constructing a detailed map of the energy levels in the system we are able to predict the importance of each layer to the open circuit voltage of the solar cell, which we then back up through measurements of the surface photovoltage of the cell under white illumination. Our results demonstrate the effectiveness of air photoemission and Kelvin probe contact potential difference measurements as a method of identifying the factors contributing to the open circuit voltage in a solar cell, as well as being an excellent way of probing the physics of new materials.
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK. gat@st-andrews.ac.uk idws@st-andrews.ac.uk.
authors.forename: J R
authors.initials: JR
authors.lastname: Harwell
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK. gat@st-andrews.ac.uk idws@st-andrews.ac.uk and KP Technology Ltd, Burn Street, Wick, Caithness KW1 5EH, UK.
authors.forename: T K
authors.initials: TK
authors.lastname: Baikie
authors.affiliation: KP Technology Ltd, Burn Street, Wick, Caithness KW1 5EH, UK.
authors.forename: I D
authors.initials: ID
authors.lastname: Baikie
authors.affiliation: EaSTChem, School of Chemistry, St Andrews University, North Haugh, KY16 9SS, UK.
authors.forename: J L
authors.initials: JL
authors.lastname: Payne
authors.affiliation: EaSTChem, School of Chemistry, St Andrews University, North Haugh, KY16 9SS, UK.
authors.forename: C
authors.initials: C
authors.lastname: Ni
authors.affiliation: EaSTChem, School of Chemistry, St Andrews University, North Haugh, KY16 9SS, UK.
authors.forename: J T S
authors.initials: JT
authors.lastname: Irvine
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK. gat@st-andrews.ac.uk idws@st-andrews.ac.uk.
authors.forename: G A
authors.initials: GA
authors.lastname: Turnbull
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK. gat@st-andrews.ac.uk idws@st-andrews.ac.uk.
authors.forename: I D W
authors.initials: ID
authors.lastname: Samuel