title: Enhanced mobility-lifetime products in PbS colloidal quantum dot photovoltaics.
abstract: Colloidal quantum dot (CQD) photovoltaics offer a promising approach to harvest the near-IR region of the solar spectrum, where half of the sun's power reaching the earth resides. High external quantum efficiencies have been obtained in the visible region in lead chalcogenide CQD photovoltaics. However, the corresponding efficiencies for band gap radiation in the near-infrared lag behind because the thickness of CQD photovoltaic layers from which charge carriers can be extracted is limited by short carrier diffusion lengths. Here, we investigate, using a combination of electrical and optical characterization techniques, ligand passivation strategies aimed at tuning the density and energetic distribution of charge trap states at PbS nanocrystal surfaces. Electrical and optical measurements reveal a more than 7-fold enhancement of the mobility-lifetime product of PbS CQD films treated with 3-mercaptopropionic acid (MPA) in comparison to traditional organic passivation strategies that have been examined in the literature. We show by direct head-to-head comparison that the greater mobility-lifetime products of MPA-treated devices enable markedly greater short-circuit current and higher power conversion efficiency under AM1.5 illumination. Our findings highlight the importance of selecting ligand treatment strategies capable of passivating a diversity of surface states to enable shallower and lower density trap distributions for better transport and more efficient CQD solar cells.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Jeong
authors.forename: Jiang
authors.initials: J
authors.lastname: Tang
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.forename: Jihye
authors.initials: J
authors.lastname: Kim
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Schaefer
authors.forename: Kyle
authors.initials: K
authors.lastname: Kemp
authors.forename: Larissa
authors.initials: L
authors.lastname: Levina
authors.forename: Xihua
authors.initials: X
authors.lastname: Wang
authors.forename: Sjoerd
authors.initials: S
authors.lastname: Hoogland
authors.forename: Ratan
authors.initials: R
authors.lastname: Debnath
authors.forename: Lukasz
authors.initials: L
authors.lastname: Brzozowski
authors.forename: Edward H
authors.initials: EH
authors.lastname: Sargent
authors.forename: John B
authors.initials: JB
authors.lastname: Asbury
mesh_terms: D003102:Colloids / Q000737:chemistry*; D011211:Electric Power Supplies; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007854:Lead / Q000737:chemistry*; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012993:Solar Energy
chemical_list: D003102:Colloids; D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead