title: Real-space observation of unbalanced charge distribution inside a perovskite-sensitized solar cell.
abstract: Perovskite-sensitized solar cells have reached power conversion efficiencies comparable to commercially available solar cells used for example in solar farms. In contrast to silicon solar cells, perovskite-sensitized solar cells can be made by solution processes from inexpensive materials. The power conversion efficiency of these cells depends substantially on the charge transfer at interfaces. Here we use Kelvin probe force microscopy to study the real-space cross-sectional distribution of the internal potential within high efficiency mesoscopic methylammonium lead tri-iodide solar cells. We show that the electric field is homogeneous through these devices, similar to that of a p-i-n type junction. On illumination under short-circuit conditions, holes accumulate in front of the hole-transport layer as a consequence of unbalanced charge transport in the device. After light illumination, we find that trapped charges remain inside the active device layers. Removing these traps and the unbalanced charge injection could enable further improvements in performance of perovskite-sensitized solar cells.
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Victor W
authors.initials: VW
authors.lastname: Bergmann
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Stefan A L
authors.initials: SA
authors.lastname: Weber
authors.affiliation: Abengoa Research, C/Energía Solar no 1, Campus Palmas Altas, Seville-41014, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Javier Ramos
authors.affiliation: Department of Chemistry and Chemical Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Mohammad Khaja
authors.initials: MK
authors.lastname: Nazeeruddin
authors.affiliation: Department of Chemistry and Chemical Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Domanski
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Lieberwirth
authors.affiliation: Abengoa Research, C/Energía Solar no 1, Campus Palmas Altas, Seville-41014, Spain.
authors.forename: Shahzada
authors.initials: S
authors.lastname: Ahmad
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Berger