An Organic D-π-A Dye for Record Efficiency Solid-State Sensitized Heterojunction Solar Cells

The high molar absorption coefficient organic D-π-A dye C220 exhibits more than 6% certified electric power conversion efficiency at AM 1.5G solar irradiation (100 mW cm<sup>−2</sup>) in a solid-state dye-sensitized solar cell using 2,2′,7,7′-tetrakis(<i>N</i>,<i>N</i>-dimethoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) as the organic hole-transporting material. This contributes to a new record (6.08% by NREL) for this type of sensitized heterojunction photovoltaic device. Efficient charge generation is proved by incident photon-to-current conversion efficiency spectra. Transient photovoltage and photocurrent decay measurements showed that the enhanced performance achieved with C220 partially stems from the high charge collection efficiency over a wide potential range.