title: Detecting trap states in planar PbS colloidal quantum dot solar cells.
abstract: The recently developed planar architecture (ITO/ZnO/PbS-TBAI/PbS-EDT/Au) has greatly improved the power conversion efficiency of colloidal quantum dot photovoltaics (QDPVs). However, the performance is still far below the theoretical expectations and trap states in the PbS-TBAI film are believed to be the major origin, characterization and understanding of the traps are highly demanded to develop strategies for continued performance improvement. Here employing impedance spectroscopy we detect trap states in the planar PbS QDPVs. We determined a trap state of about 0.34 eV below the conduction band with a density of around 3.2 × 1016cm-3eV-1. Temperature dependent open-circuit voltage analysis, temperature dependent diode property analysis and temperature dependent build-in potential analysis consistently denotes an below-bandgap activation energy of about 1.17-1.20 eV.
authors.affiliation: Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, P.R. China.
authors.forename: Zhiwen
authors.initials: Z
authors.lastname: Jin
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Aiji
authors.initials: A
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, P.R. China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Yinshu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, P.R. China.
authors.forename: Jizheng
authors.initials: J
authors.lastname: Wang