Towards anode with low indium content as effective anode in organic solar cells

► The manuscript is dedicated to the realization of anode with low indium content. ► We show that a very thin In2O3 film deposited onto another transparent conductive oxide (TCO=ZnO, SnO2) allows to improve the contact between the TCO and the organic material. ► Optima results are achieved when a thin MoO3 thin film is added to these bilayer structures. In2O3 thin films (100nm thick) have been deposited by reactive evaporation of indium, in an oxygen partial atmosphere. Conductive (σ=3.5×103S/cm) and transparent films are obtained using the following experimental conditions: oxygen partial pressure=1×10−1Pa, substrate temperature=300°C and deposition rate=0.02nm/s. Layers of this In2O3 thick of 5nm have been introduced in AZO/In2O3 and FTO/In2O3 multilayer anode structures. The performances of organic photovoltaic cells, based on the couple CuPc/C60, are studied using the anode as parameter. In addition to these bilayers, other structures have been used as anode: AZO, FTO, AZO/In2O3/MoO3, FTO/In2O3/MoO3 and FTO/MoO3. It is shown that the use of the In2O3 film in the bilayer structures improves significantly the cell performances. However the open circuit voltage is quite small while better efficiencies are achieved when MoO3 is present. These results are discussed in the light of surface roughness and surface work function of the different anodes.