Organo-metal halide perovskite-based solar cells with CuSCN as the inorganic hole selective contact

Abstract

CuSCN is proposed as a cost-competitive hole selective contact for the emerging organo-metal halide perovskite-based solar cells. The CuSCN films have been deposited by a solution casting technique, which has proven to be compatible with the perovskite films, obtaining planar-like heterojunction-based glass/FTO/TiO₂/CH₃NH₃PbI_3−xCl_x/CuSCN/Au solar cells with a power conversion efficiency of 6.4%. Among the photovoltaic parameters, the fill factor (i.e. 62%) suggests good carrier selectivity and, therefore, efficient functionality of the TiO₂ and CuSCN charge carrier selective contacts. However, the open-circuit voltage (V_oc), which remains low in comparison with the state of the art perovskite-based solar cells, appears to be the main limiting parameter. This is attributed to the short diffusion length as determined by impedance spectroscopy. However, the recombination losses are not only affected by the CuSCN, but also by the perovskite film. Indeed, variations of 20 °C in the thermal annealing of the perovskite films result in changes larger than 200 mV in the V_oc. Furthermore, a detailed analysis of the quantum efficiency spectra contributes significant insights into the influence of the selective contacts on the photocurrent of the planar heterojunction perovskite solar cells.