title: Carrier separation and transport in perovskite solar cells studied by nanometre-scale profiling of electrical potential.
abstract: Organometal-halide perovskite solar cells have greatly improved in just a few years to a power conversion efficiency exceeding 20%. This technology shows unprecedented promise for terawatt-scale deployment of solar energy because of its low-cost, solution-based processing and earth-abundant materials. We have studied charge separation and transport in perovskite solar cells-which are the fundamental mechanisms of device operation and critical factors for power output-by determining the junction structure across the device using the nanoelectrical characterization technique of Kelvin probe force microscopy. The distribution of electrical potential across both planar and porous devices demonstrates p-n junction structure at the TiO2/perovskite interfaces and minority-carrier diffusion/drift operation of the devices, rather than the operation mechanism of either an excitonic cell or a p-i-n structure. Combining the potential profiling results with solar cell performance parameters measured on optimized and thickened devices, we find that carrier mobility is a main factor that needs to be improved for further gains in efficiency of the perovskite solar cells.
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Chun-Sheng
authors.initials: CS
authors.lastname: Jiang
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Mengjin
authors.initials: M
authors.lastname: Yang
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Bobby
authors.initials: B
authors.lastname: To
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Sanjini U
authors.initials: SU
authors.lastname: Nanayakkara
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Luther
authors.affiliation: Advanced Materials Research Institute, University of New Orleans, New Orleans, Louisiana 70148, USA.
authors.forename: Weilie
authors.initials: W
authors.lastname: Zhou
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Berry
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Jao
authors.initials: J
authors.lastname: van de Lagemaat
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Nitin P
authors.initials: NP
authors.lastname: Padture
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhu
authors.affiliation: National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, USA.
authors.forename: Mowafak M
authors.initials: MM
authors.lastname: Al-Jassim