Sub-nanometer Ga2O3 tunnelling layer by atomic layer deposition to achieve 1.1V open-circuit potential in dye-sensitized solar cells

Herein, we present the first use of a gallium oxide tunnelling layer to significantly reduce electron recombination in dye-sensitized solar cells (DSC). The sub-nanometer coating is achieved using atomic layer deposition (ALD) and leading to a new DSC record open-circuit potential of 1.1V with state-of-the-art organic D-π-A sensitizer and cobalt redox mediator. After ALD of only a few angstroms of Ga2O3, the electron back reaction is reduced by more than an order of magnitude while charge collection efficiency and fill factor are increased by 30% and 15% respectively. The photo-generated exciton separation processes of electron injection into the TiO2 conduction band and the hole injection into the electrolyte are characterized in detail.