Phenanthroline-Based\nLow-Cost and Efficient Small-Molecule\nCathode Interfacial Layer Enables High-Performance Inverted Perovskite\nSolar Cells via Doctor-Blade Coating

Perovskite solar cells (PSCs) have recently emerged as\nhighly efficient\nand cutting-edge photovoltaic technology. In inverted PSCs, challenges\nare focused on the insufficient interface contact and energy level\nmisalignment between the electron transport layer (ETL) and the metal\nelectrode. Hence, the cathode interfacial layer (CIL) plays a crucial\nrole in regulating energy levels and enabling charge extraction in\nPSCs. In this study, a low-cost phenanthroline derivative, 4,7-dimethoxy-1,10-phenanthroline\n(Phen-OMe), is developed as an efficient CIL between the PCBM and\nAg electrodes. The incorporation of Phen-OMe not only improves the\ninterfacial contact but also effectively reduces the work function\n(WF) of the Ag electrode, thus promoting charge dissociation and transport\nat the interface. Through utilizing a wide-band-gap perovskite with\nthe band gap of 1.77 eV as the active layer by a simple, high-throughput,\nand low-cost doctor-blade coating process, the power conversion efficiency\n(PCE) is enhanced significantly from 16.11% of the control device\nto 18.61% of the device with Phen-OMe as the CIL. Interestingly, Phen-OMe\nshows a broad application as the CIL in PSCs and tandem solar cells\n(TSCs), resulting in a boosted efficiency of 22.29% in intermediate-band-gap\nPSCs and a PCE of 22.05% with a high open-circuit voltage (<i>V</i><sub>OC</sub>) of 2.12 V in the perovskite/organic TSC.\nThis achievement shows that Phen-OMe would be a potential candidate\nas low-cost and efficient CILs for PSCs.