title: Water Splitting with Series-Connected Polymer Solar Cells.
abstract: We investigate light-driven electrochemical water splitting with series-connected polymer solar cells using a combined experimental and modeling approach. The expected maximum solar-to-hydrogen conversion efficiency (ηSTH) for light-driven water splitting is modeled for two, three, and four series-connected polymer solar cells. In the modeling, we assume an electrochemical water splitting potential of 1.50 V and a polymer solar cell for which the external quantum efficiency and fill factor are both 0.65. The minimum photon energy loss (Eloss), defined as the energy difference between the optical band gap (Eg) and the open-circuit voltage (Voc), is set to 0.8 eV, which we consider a realistic value for polymer solar cells. Within these approximations, two series-connected single junction cells with Eg= 1.73 eV or three series-connected cells with Eg= 1.44 eV are both expected to give an ηSTHof 6.9%. For four series-connected cells, the maximum ηSTHis slightly less at 6.2% at an optimal Eg= 1.33 eV. Water splitting was performed with series-connected polymer solar cells using polymers with different band gaps. PTPTIBDT-OD (Eg= 1.89 eV), PTB7-Th (Eg= 1.56 eV), and PDPP5T-2 (Eg= 1.44 eV) were blended with [70]PCBM as absorber layer for two, three, and four series-connected configurations, respectively, and provide ηSTHvalues of 4.1, 6.1, and 4.9% when using a retroreflective foil on top of the cell to enhance light absorption. The reasons for deviations with experiments are analyzed and found to be due to differences in Egand Eloss. Light-driven electrochemical water splitting was also modeled for multijunction polymer solar cells with vertically stacked photoactive layers. Under identical assumptions, an ηSTHof 10.0% is predicted for multijunction cells.
authors.affiliation: Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Serkan
authors.initials: S
authors.lastname: Esiner
authors.affiliation: Simbeyond B.V. , P.O. Box 513, NL 5600 MB Eindhoven, The Netherlands.
authors.forename: Harm
authors.initials: H
authors.lastname: van Eersel
authors.affiliation: Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Gijs W P
authors.initials: GW
authors.lastname: van Pruissen
authors.affiliation: BASF Schweiz AG , Schwarzwaldallee 215, CH-4002 Basel, Switzerland.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Turbiez
authors.affiliation: Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.|Dutch Institute for Fundamental Energy Research , De Zaale 20, 5612 AJ Eindhoven, The Netherlands.
authors.forename: Martijn M
authors.initials: MM
authors.lastname: Wienk
authors.affiliation: Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.|Dutch Institute for Fundamental Energy Research , De Zaale 20, 5612 AJ Eindhoven, The Netherlands.
authors.forename: René A J
authors.initials: RA
authors.lastname: Janssen
keywords: fullerene; light-driven electrochemical water splitting; organic photovoltaics; overpotential; semiconducting polymer; solar-to-hydrogen conversion