Exploring the Interactions at the Interface: Tailoring Carbazole‐Based Self‐Assembled Molecules with Varying Functional Groups for Enhancing the Performance of Inverted Perovskite Solar Cells

Abstract

Four different carbazole‐based self‐assembled molecules (SAMs) with different terminal groups have been designed and synthesized as hole‐selective contacts for inverted perovskite solar cells to investigate their interfacial interactions and, consequently, the performance of the devices. Using the carbazole core as a reference, the effect of the thiophen‐2‐yl phenyl, or the hydroxymethyl phenyl attached to the core through a phenyl moiety, with that of the thiophene directly linked to the carbazole is compared. These new SAMs have been successfully synthesized using cost‐effective starting materials and a straightforward synthetic method, eliminating the need for expensive and complex purification processes. Subsequently, they have been applied as efficient hole‐selective contact in inverted perovskite solar cells, leading to an outstanding power conversion efficiency of 19.67% in the case of SAM5, containing a carbazole‐core substituted with double 2‐phenylthiophene side arms as functional group. The detailed characterization of the interface and the charge kinetics has allowed to determine the effect of each substituent.