Fluorine doped zinc tin oxide multilayer transparent conducting Oxides for organic photovoltaic's Cells

Few nm of Ag layer embedded in fluorine doped zinc tin oxide FZTO/Ag/FZTO was fabricated on glass by radio frequency magnetron sputtering at room temperature for the applications of organic photovoltaic's cells. The structural, electrical and optical properties of FZTO thin films were investigated. The multilayer of the FZTO (40 nm)/Ag (9 nm)/FZTO (40 nm) electrode shows the maximum optical transmittance (λ=380-770 nm) of 88.15%, quite low electrical resistivity of ∼8×10^-5 Ω cm and the corresponding figure of merit (T¹⁰/R_sq) is equivalent to 3.46×10^-2 Ω^-1. A normal organic photovoltaic's (OPV) structure of poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b]dithiophene-2,6-diyl][3-fluoro-2-[(2 ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7): phenyl-C70-butyric acid methyl ester (PC70BM) was fabricated on glass/FZTO/Ag/FZTO to examine the compatibility of OPV as a transparent conducting electrode. The bulk hetero-junction organic photovoltaic's device fabricated on the multilayer FAF electrode exhibited open circuit voltage (V_oc) of 0.72 V, a short circuit current (J_sc) of 12.28 mA/cm², a fill factor (FF) of 0.54. These properties are analogous to V_oc=0.75 V, J_sc=14.87 mA/cm², FF=0.53 on commercial indium tin oxide (ITO). A resultant power conversion efficiency of 4.84% is comparable with the 5.90% of the same OPV structure on the commercial ITO as a reference. This reveals that FZTO/Ag/FZTO multilayer electrode is a promising electrode scheme for bulk hetero-junction organic photovoltaic's cells (BHJ-OPVs).