Spray Deposition of Silver Nanowire Electrodes for Semitransparent Solid-State Dye-Sensitized Solar Cells

Transparent top electrodes for solid-state dye-sensitized solar cells (ssDSCs) allow for fabrication of mechanically stacked ssDSC tandems, partially transparent ssDSCs for building integration, and ssDSCs on metal foil substrates. A solution-processed, highly transparent, conductive electrode based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)] and spray-deposited silver nanowires (Ag NWs) is developed as an effective top contact for ssDSCs. The electrode is solution-deposited using conditions and solvents that do not damage or dissolve the underlying ssDSC and achieves high performance: a peak transmittance of nearly 93% at a sheet resistance of 18 /square - all without any annealing that would harm the ssDSC. The role of the PEDOT:PSS in the electrode is twofold: it ensures ohmic contact between the ssDSC 2,2,7,7-tetrakis-(N,N-di-p-methoxyphenylamine)9,9-spirobifluorene (Spiro-OMeTAD) overlayer and the silver nanowires and it decreases the series resistance of the device. Semitransparent ssDSCs with D35 dye fabricated using this Ag NW/PEDOT:PSS transparent electrode show power conversion efficiencies of 3.6%, nearly as high as a reference device using an evaporated silver electrode (3.7%). In addition, the semitransparent ssDSC shows high transmission between 700-1100 nm, a necessity for use in efficient tandem devices. Such an electrode, in combination with efficient ssDSCs or hybrid perovskite-sensitized solar cells, can allow for the fabrication of efficient, cost-effective tandem photovoltaics.