Introduction of Graphene Oxide as Buffer Layer in Perovskite Solar Cells and the Promotion of Soluble n-Butyl-substituted Copper Phthalocyanine as Efficient Hole Transporting Material

Organometal halide perovskite solar cells have been constructed using soluble tetra-n-butyl-copper phthalocyanine as hole transporting material. Devices were constructed and characterized under ambient conditions of 50–60% ambient humidity. Soluble copper phthalocyanine gave a modest PCE of 7.3% but when a buffer layer of either Al₂O₃ or graphene oxide was introduced between the perovskite and the hole transporting layer the cell efficiency extensively increased and reached 14.4% in the presence of graphene oxide. Corresponding data obtained by employing the standard spiro-OMeTAD as hole transporter gave equivalent performance. Combination then of tetra-n-butyl-copper phthalocyanine with graphene oxide offers a very good alternative of simpler and stable materials for perovskite solar cell construction. The presently recorded data highlight the role of the buffer layer, especially graphene oxide, as the material which blocks shunt paths and facilitates hole transfer between the perovskite and the hole transporting layer.