title: Colloidal PbS quantum dot solar cells with high fill factor.
abstract: We fabricate PbS colloidal quantum dot (QD)-based solar cells using a fullerene derivative as the electron-transporting layer (ETL). A thiol treatment and oxidation process are used to modify the morphology and electronic structure of the QD films, resulting in devices that exhibit a fill factor (FF) as high as 62%. We also show that, for QDs with a band gap of less than 1 eV, an open-circuit voltage (VOC) of 0.47 V can be achieved. The power conversion efficiency reaches 1.3% under 1 sun AM1.5 test conditions and 2.4% under monochromatic infrared (lambda=1310 nm) illumination. A consistent mechanism for device operation is developed through a circuit model and experimental measurements, shedding light on new approaches for optimization of solar cell performance by modifying the interface between the QDs and the neighboring charge transport layers.
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Ni
authors.initials: N
authors.lastname: Zhao
authors.forename: Tim P
authors.initials: TP
authors.lastname: Osedach
authors.forename: Liang-Yi
authors.initials: LY
authors.lastname: Chang
authors.forename: Scott M
authors.initials: SM
authors.lastname: Geyer
authors.forename: Darcy
authors.initials: D
authors.lastname: Wanger
authors.forename: Maddalena T
authors.initials: MT
authors.lastname: Binda
authors.forename: Alexi C
authors.initials: AC
authors.lastname: Arango
authors.forename: Moungi G
authors.initials: MG
authors.lastname: Bawendi
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bulovic