title: The donor-supply electrode enhances performance in colloidal quantum dot solar cells.
abstract: Colloidal quantum dot (CQD) solar cells combine solution-processability with quantum-size-effect tunability for low-cost harvesting of the sun's broad visible and infrared spectrum. The highest-performing colloidal quantum dot solar cells have, to date, relied on a depleted-heterojunction architecture in which an n-type transparent metal oxide such as TiO2 induces a depletion region in the p-type CQD solid. These devices have, until now, been limited by a modest depletion region depth produced in the CQD solid owing to limitations in the doping available in TiO2. Herein we report a new device geometry-one based on a donor-supply electrode (DSE)-that leads to record-performing CQD photovoltaic devices. Only by employing this new charge-extracting approach do we deepen the depletion region in the CQD solid and thereby extract notably more photocarriers, the key element in achieving record photocurrent and device performance. With the use of optoelectronic modeling corroborated by experiment, we develop the guidelines for building a superior CQD solar cell based on the DSE concept. We confirm that using a shallow-work-function terminal electrode is essential to producing improved charge extraction and enhanced performance.
authors.affiliation: Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3G4, Canada.
authors.forename: Pouya
authors.initials: P
authors.lastname: Maraghechi
authors.forename: André J
authors.initials: AJ
authors.lastname: Labelle
authors.forename: Ahmad R
authors.initials: AR
authors.lastname: Kirmani
authors.forename: Xinzheng
authors.initials: X
authors.lastname: Lan
authors.forename: Michael M
authors.initials: MM
authors.lastname: Adachi
authors.forename: Susanna M
authors.initials: SM
authors.lastname: Thon
authors.forename: Sjoerd
authors.initials: S
authors.lastname: Hoogland
authors.forename: Anna
authors.initials: A
authors.lastname: Lee
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Ning
authors.forename: Armin
authors.initials: A
authors.lastname: Fischer
authors.forename: Aram
authors.initials: A
authors.lastname: Amassian
authors.forename: Edward H
authors.initials: EH
authors.lastname: Sargent
mesh_terms: D011211:Electric Power Supplies; D004566:Electrodes; D004579:Electron Transport; D004867:Equipment Design; D019544:Equipment Failure Analysis; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D045663:Quantum Dots; D012993:Solar Energy; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium