Oxygen-induced doping of spiro-MeOTAD in solid-state dye-sensitized solar cells and its impact on device performance.
Solid state dye-sensitized solar cells (sDSCs) employing the hole conductor 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD) require the presence of oxygen during fabrication and storage. In this paper, we determine the concentrations of oxidized spiro-MeOTAD within devices under different operating and storage conditions by UV-vis spectroscopy. Relative concentrations of spiro-MeOTAD(+) were found to be greater than 10% after illumination for standard sDSCs, where no chemical dopant had been used in the solar cell fabrication but oxygen and lithium ions were present. We suggest that oxidized spiro-MeOTAD is created as a byproduct of oxygen reduction at the TiO(2) surface during cell illumination. Furthermore, we studied the effect of light soaking under different conditions and associated changes in spiro-MeOTAD(+) concentration on the solar cell measurements. Our findings give insights to photochemical reactions occurring within sDSCs and provide guidelines for which doping levels should be used in device fabrication in absence of oxygen.
Department of Materials Engineering, Monash University, Victoria 3800, Australia. u.cappel@imperial.ac.uk
Ute B
UB
Cappel
Torben
T
Daeneke
Udo
U
Bach
D011211:Electric Power Supplies; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005449:Fluorenes / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010100:Oxygen / Q000737:chemistry*; D010316:Particle Size; D012993:Solar Energy
D005449:Fluorenes; D005456:Fluorescent Dyes; C041509:fluorene; D010100:Oxygen