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Liquid State and Zombie Dye Sensitized Solar Cells with Copper Bipyridine Complexes Functionalized with Alkoxy Groups
journal contribution
posted on 2020-03-19, 11:36 authored by Yasemin Saygili, Marko Stojanovic, Hui-Seon Kim, Joel Teuscher, Rosario Scopelliti, Marina Freitag, Shaik M. Zakeeruddin, Jacques-E. Moser, Michael Grätzel, Anders HagfeldtCopper
redox mediators can be employed in dye sensitized solar
cells (DSCs) both as liquid electrolytes or as solid state hole transport
materials (HTMs). The solid state devices that employ copper complex
HTMs can be simply obtained by solvent evaporation in liquid state
devices. During this evolution, the copper complex molecules present
in the electrolyte solvent slowly aggregate in the pores of the TiO2 film and also close the gap between the TiO2 film
and counter electrode. However, the crystallization of the HTM that
infiltrated in the mesoscopic TiO2 pores can lead to low
photovoltaic performance. In order to prevent this problem, we designed
two copper redox mediators [Cu(beto)2]1+ (beto
= 4,4′-diethoxy-6,6′-dimethyl-2,2′-bipyridine)
and [Cu(beto2Ox)2]1+ (beto2Ox = 4,4′-bis(2-methoxyethoxy)-6,6′-dimethyl-2,2′-bipyridine)
with extended side chains. First, we studied these complexes in liquid
state devices in reference to the [Cu(tmby)2]2+/1+ complex (tmby = 4,4′,6,6′- tetramethyl-2,2′-bipyridine).
The solar-to- electrical power conversion efficiencies for liquid
state devices were over 10% for all of the complexes by using the
organic Y123 dye under 1000 Wm–2 AM1.5G illumination.
However, solid state devices showed significantly diminished charge
transport properties and short circuit current density values even
though the crystallization was reduced.