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.