A series of D-π-A organic dyes, X72-75, containing novel triarylamine electron donors have been synthesized for dye-sensitized solar cells (DSCs). The superiority of the asymmetric design of the triphenylamine electron donor over the symmetrical triphenylamine when applied in organic dyes for cobalt cells has been observed. Using X72 with the cobalt(II/III) redox shuttle resulted in an overall power conversion efficiency (PCE) of 9.18%, outperforming the state-of-the-art dye C218 under the same conditions.