Through elongating the end or side alkyl chains of dye molecules, we decorate anatase nanocrystals with a thicker organic assembly featuring a smaller tilt angle of the D–π-A backbone with respect to the surface normal, which retards the interfacial charge recombination and confers a higher photovoltage output on mesoscopic cobalt solar cells displaying an over 10% power conversion efficiency at the AM1.5G conditions.