Efficient tandem polymer photovoltaic cells using inorganic metal oxides as a transparent middle connection unit

A kind of tandem polymer photovoltaic cell with inorganic metal oxides as a transparent middle connection unit to link the two subcells having different absorption characteristics is developed and its open-circuit voltage origin is investigated. The middle connection unit consists of an electron-transporting titanium oxide (TiOx) layer, a thin aluminum (Al) layer and a hole-transporting molybdenum oxide (MoO3) layer. The inserted thin Al layer between the TiOx and MoO3 layers not only acts as an efficient recombination site for electrons and holes photo-generated in the two subcells, but also realigns the electronic energy levels at TiOx/MoO3 interfaces to reduce the open-circuit voltage loss. The open-circuit voltage of the tandem cell is the summation of the two subcells.