Enhanced Charge Transfer in Atom‐Thick 2H–WS2 Nanosheets' Electron Transport Layers of Perovskite Solar Cells.

The structure and the electronic properties of the electron‐transport layer (ETL) of perovskite solar cells (PSCs) govern the interfacial charge transfer and charge transportation to the electrode. The ETLs of two dimensions, that are atom thick, and have a planar structure that possesses special electronic properties, such as the surface collective motion of excitons or charge transfer–driven defect state relief, that is 2D transition metal dichalcogenide, allow a highly energetic carrier dynamic process for enhanced photovoltaic effect. Herein, it is discovered that planar, few‐atom‐thick 2H–WS2 nanosheets' ETLs drive ultrafast charge transfer and transportation along the ETL during the photovoltaic process. Time‐resolved photoluminescence and electrochemical impedance spectroscopy analysis results indicate that the charge transfer from the perovskite to the ETL occurs as fast as 5.9 ns with charge transfer resistance as low as 25.6 Ω. This allows the PSC device to produce a power conversion efficiency of 18.21% with short‐circuit current density, open‐circuit voltage, and fill factor as high as 22.24 mA cm2, 1.12 V, and 0.731, respectively. The PSC retains 96.87% of its performance when being aged in nitrogen atmosphere for 33 days. Atom‐thick planar WS2 ETL nanosheets can be the basis for the development of high‐performance PSC devices. [ABSTRACT FROM AUTHOR]