Unveiling and overcoming the interfacial degradation between CuSCN and metal electrodes in perovskite solar cells

Abstract

Copper(I) thiocyanate (CuSCN) is an extremely cheap and intrinsically stable p-type hole transport material which is attractive for solar cell applications. However, its devices exhibit poor stability due to the severe degradation at the CuSCN/metal-electrode interface and the origin is still unclear. Herein, the underlying degradation mechanism at CuSCN/metal (including Au, Ag and Al) interfaces is well unveiled, and metal electrodes induce the self-disproportionation reaction of Cu⁺ in CuSCN (Cu⁺ = Cu⁰ + Cu²⁺) through the alloying of Cu/metal, contributing to the interfacial degradation. This process in devices is spontaneous and sharply accelerated under the electric field, namely actual operation state. Thus, the metal electrode was replaced by a chemically stable carbon electrode to overcome the interface degradation, enabling efficient and stable n–i–p perovskite solar cells. Our finding uncovers the secret of degradation at the CuSCN/metal-electrode interface and provides an insight into the potential application of CuSCN in photoelectric devices, especially in solar cells.