Perylenediimide-based bridged dimers as electron-transport layers in perovskite solar cells with p–i–n configuration

Fullerene derivative PCBM is a widely used electron transport layer (ETL) in p–i–n structured perovskite solar cells (PSCs). However, the high cost of PCBM, often exceeding that of all other active materials combined (excluding ITO), represents a significant barrier to the large-scale commercialization of PSCs, necessitating the search for more cost-effective alternatives. Herein, nine novel perylenediimide (PDI) dimers are synthesized and employed as ETLs to overcome these challenges. Electrochemical, optoelectronic, and morphological properties of the synthesized compounds were systematically compared with respect to the reference PDI derivative with a thiophene core building block. Correlations were identified between the ability of the developed materials to form high-quality, uniform films and the stabilization of the underlying perovskite layer. A further significant correlation was also observed between the LUMO level of the PDI derivative and the performance of the perovskite devices. These findings offer valuable insights into the targeted design of dimeric perylenediimide derivatives for creating stable and efficient perovskite solar cells.