title: Charge-extraction strategies for colloidal quantum dot photovoltaics.
abstract: The solar-power conversion efficiencies of colloidal quantum dot solar cells have advanced from sub-1% reported in 2005 to a record value of 8.5% in 2013. Much focus has deservedly been placed on densifying, passivating and crosslinking the colloidal quantum dot solid. Here we review progress in improving charge extraction, achieved by engineering the composition and structure of the electrode materials that contact the colloidal quantum dot film. New classes of structured electrodes have been developed and integrated to form bulk heterojunction devices that enhance photocharge extraction. Control over band offsets, doping and interfacial trap state densities have been essential for achieving improved electrical communication with colloidal quantum dot solids. Quantum junction devices that not only tune the optical absorption spectrum, but also provide inherently matched bands across the interface between p- and n-materials, have proven that charge separation can occur efficiently across an all-quantum-tuned rectifying junction.
authors.affiliation: 1] Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada [2] School of Materials Science and Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, Anhui Province, 230009, China.
authors.forename: Xinzheng
authors.initials: X
authors.lastname: Lan
authors.affiliation: 1] Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada [2] Solar and Photovoltaic Engineering Research Center, King Abdullah University of Science and Technology, 4700 Thuwal 23955-6900, Saudi Arabia.
authors.forename: Silvia
authors.initials: S
authors.lastname: Masala
authors.affiliation: Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Sargent