In this work, a facile and low-temperature water evaporation approach to prepare columnar superstructures consisting of face centered cubic (fcc) Cu2-xSe nanoflakes stacked along 111 direction is reported. Formation of such unique stacked nanoflake assemblies is resulted from oriented attachment of isolated hexagonal CuSe nanoflakes along the 001 direction with a ripening effect driven by solvent evaporation, and then followed by a phase conversion into fcc Cu2-xSe. Evolution from hexagonal CuSe nanoflakes to fcc Cu2-xSe columnar superstructures results in obvious red-shift of band-gap absorption edge from 670 to 786 nm and dramatically decreased Raman resonance band intensity of the Se-Se stretching mode at 259 cm(-1) due to the phase conversion and composition variation. Remarkably, the Cu2-xSe columnar superstructures are employed as low-cost and highly efficient counter electrodes (CEs) in quantum dot sensitized solar cells, exhibiting excellent electrocatalytic activity for polysulfide electrolyte regeneration. A ZnSe/CdSe cosensitized solar cell using the Cu2-xSe CE shows a significant increase in fill factor and short-current density (J(SC)) and yields a 128% enhancement in power conversion efficiency as compared to the traditional noble metal Pt CE.