title: A quantitative model for charge carrier transport, trapping and recombination in nanocrystal-based solar cells.
abstract: Improving devices incorporating solution-processed nanocrystal-based semiconductors requires a better understanding of charge transport in these complex, inorganic-organic materials. Here we perform a systematic study on PbS nanocrystal-based diodes using temperature-dependent current-voltage characterization and thermal admittance spectroscopy to develop a model for charge transport that is applicable to different nanocrystal-solids and device architectures. Our analysis confirms that charge transport occurs in states that derive from the quantum-confined electronic levels of the individual nanocrystals and is governed by diffusion-controlled trap-assisted recombination. The current is limited not by the Schottky effect, but by Fermi-level pinning because of trap states that is independent of the electrode-nanocrystal interface. Our model successfully explains the non-trivial trends in charge transport as a function of nanocrystal size and the origins of the trade-offs facing the optimization of nanocrystal-based solar cells. We use the insights from our charge transport model to formulate design guidelines for engineering higher-performance nanocrystal-based devices.
authors.affiliation: Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich 8092, Switzerland.
authors.forename: Deniz
authors.initials: D
authors.lastname: Bozyigit
authors.affiliation: Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich 8092, Switzerland.
authors.forename: Weyde M M
authors.initials: WM
authors.lastname: Lin
authors.affiliation: Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich 8092, Switzerland.
authors.forename: Nuri
authors.initials: N
authors.lastname: Yazdani
authors.affiliation: Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich 8092, Switzerland.
authors.forename: Olesya
authors.initials: O
authors.lastname: Yarema
authors.affiliation: Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich 8092, Switzerland.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Wood