Previous reports have observed a direct relationship between the polymer poly(3-hexylthiophene) molecular weight (MW) and the perovskite solar cell (PSC) efficiency. Herein, we analyse how the differences in MW and the differences in energetic disorder influence the interfacial carrier losses in the PSCs under operation conditions and explain the observed differences. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'.
Keywords: charge extraction; energetic disorder; perovskite solar cells; photo-induced transient photovoltage; poly(3-hexylthiophene).