Easy processing carbon paper electrode for highly efficient perovskite solar cells

Perovskite solar cells are by far the photovoltaic technology with the fastest efficiency evolution, reaching now the astonishing power conversion efficiency (PCE) of 25.2%. Their advantages cover also color and transparency, extremely low thickness, low cost, simple fabrication methods and versatile designs. Nevertheless, since it is a young technology, there are still several challenges that need to be overcome for making its commercialization feasible. For making perovskite solar modules, the back-contact plays a critical job since it drives and deliveries the low energy electrons to the p contact of the cell. In n-i-p configuration cells, gold is normally used as back-contact, which is expensive and rare. In this work, several commercial carbon papers and application procedures were investigated. The best performing system produced 89% of the PCE obtained with standard gold back-contact. Besides having a much simpler and cheaper application method, other features such as low cost, great chemical and mechanical stability and low electrical resistivity proved carbon papers potential for commercialization. Moreover, when a gold interlayer of 5 nm was applied, the relative PCE increased up to 92%.