The dye-sensitized Zn2SnO4 solar cells were treated with Al3+ ions to enhance the power conversion efficiency for the first time. Usually, the surface treatment on photoanodes with Al3+ ions generated an overlayer of Al2O3. For Zn2SnO4 photoanode, another reaction pathway was found. The treatment with Al3+ ions led to decreasing open circuit voltage, and a 22.6% enhancement of efficiency. Mott-Schottky measurements revealed that the flat band of Zn2SnO4 had a positive shift owing to the introduction of Al3+ ions. XPS confirmed that Al3+ ions were introduced into the lattice of Zn2SnO4 and occupied the position of Se, resulting in decreased conduction band edge. TEM demonstrated the size of Zn2SnO4 nanoparticles became larger due to the reaction of Al3+ with Zn2SnO4. Although the adsorption amounts of dyes lowered by 21%, the driving force for electron injection was greatly enhanced as a result of decreased conduction band edge, resulting in significantly enhanced cell efficiency. (C) 2011 Elsevier Ltd. All rights reserved.