title: Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe-ZnO Tunnel Junction.
abstract: We developed a monolithic CdTe-PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (Eg= 1.5 eV)-PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe-PbS tandem devices by developing a ZnTe-ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm2in prototype devices.
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.|Department of Physics, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Crisp
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.|Department of Electrical, Computer, and Energy Engineering, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Pach
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.
authors.forename: J Matthew
authors.initials: JM
authors.lastname: Kurley
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: France
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Reese
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Sanjini U
authors.initials: SU
authors.lastname: Nanayakkara
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Bradley A
authors.initials: BA
authors.lastname: MacLeod
authors.affiliation: Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.|Center for Nanoscale Materials, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Dmitri V
authors.identifier: 0000-0002-6414-8587
authors.initials: DV
authors.lastname: Talapin
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Matthew C
authors.identifier: 0000-0002-2711-1355
authors.initials: MC
authors.lastname: Beard
authors.affiliation: National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
authors.forename: Joseph M
authors.identifier: 0000-0002-4054-8244
authors.initials: JM
authors.lastname: Luther
keywords: Multijunction; nanocrystals; photovoltaics; quantum dots; solar cell; tandem