Incorporating a naphthalene diimide polymer into a fullerene electron-transport layer to improve the fracture energy of perovskite solar cells

Abstract

By blending a naphthalene diimide polymer into C₆₀, we made a solution-processed electron-transport layer (ETL) for perovskite solar cells with fracture energies of 1.25 J m⁻², over 3× higher than that of thermally evaporated C₆₀. Fracture energies were measured in a double cantilever beam configuration, and fracture surface images showed a fracture location near the ETL/perovskite interface, indicating a toughening of the interface between the ETL and Ag. We show that this modification to the ETL has no adverse effect on solar cell performance, and highlight the additional benefit of reduced parasitic absorption; a finding relevant for tandem solar cells.