Insoluble Organics as Electron-Transporting Materials Enabled by Solvothermal Technology for Solution-Processable Perovskite Solar Cells

Abstract

Introducing electron transport materials (ETMs) into perovskite solar cells (PSCs) has opened up a new avenue to improve device efficiency. However, the most commonly used method of introducing ETMs still relies on a high-vacuum process due to their poor solubility, which prevents the application of ETMs in full solution-processable PSCs. Here, solvothermal technology is employed to treat the insoluble perylene diimide (PDI) molecule, giving the typical n-type organic semiconductor its soluble properties. The as-obtained products (PDI-CDs) as ETMs not only are suitable for the preparation of solution-processable PSCs but also have matched energy levels with adjacent components in the device. The appearance of oxygen-containing functional groups enables PDI-CDs to chelate uncoordinated Pb, suppressing interfacial recombination and improving efficiency by passivating the surface defects of perovskite crystals. The all-air processed carbon-based PSCs modified with PDI-CDs achieved a respectable power conversion efficiency of 11.90%.

Single‐Layer Carbon Nitride as an Efficient Metal‐Free Organic Electron‐Transport Material with a Tunable Work Function

“…[27,28] Thiazole-modified GCN sheets were tested as a metal-free ETL in inverted perovskite solar cells. [29] In situ growth of GCN films on TiO 2 ETLs of OPV cells was reported to passivate surface defects of titania, resulting in a remarkable improvement in the open-circuit voltage, exceeding 1 V. [30] Similarly, the GCN species passivated defects on grain boundaries in perovskite absorbers, [31][32][33][34] as well as on perovskite/ETL [32,35,36] and perovskite/HTL interfaces. [33] Modification of SnO 2 ETL with GCN enhanced its conductivity and simultaneously passivated defects in the perovskite absorber.…”

“…Typically, a-few-layer GCN sheets are formed by sonication-assisted approaches [23,27,29] which provide limited control over the concentration, characteristics, and stability of the inks. Alternative approaches including thermal etching, [34] intercalation, [26,33,36] supercritical treatment, [25,26,35,36] or sacrificial templates, [31] result in multi-step procedures with low yields of the GCN inks. Only a few reports showed the feasibility of producing single-layer carbon nitride (SLCN), however, the adaptation of such approaches for making application-ready SLCN inks remains a major challenge.…”