Regulating Interfacial Coupling and Electron Transport for Efficient Electron-Transporting Materials

Herein, naphthalimide derivative NDI-ID, a promising organic electron-transporting material (ETM), is used as a model molecular skeleton to investigate how the electron transport of organic ETMs and the interfacial coupling between organic ETM and perovskite are regulated by intermolecular van der Waals interactions. As shown in our computations, the van der Waals interactions between ETM and perovskite are strengthened considerably by the pi-extended modification of naphthalimide derivatives, enhancing the ETM-perovskite interfacial coupling and thus accelerating electron extraction and transfer from perovskites to ETMs by coupling of lead pi-orbitals in perovskites with pi-conjugated antibonding orbitals of ETMs. Meanwhile, the ETM intermolecular pi-pi interactions are also significantly enhanced, which stabilizes the face-to-face stacking between ETM molecules. The enhancement of the ETM intermolecular pi-pi interactions and the ETM-perovskite interfacial coupling improve remarkably the performance of ETMs. Modified naphthalimide derivative, NF2X-ID, has a very high electron mobility of 0.386 cm(2 )V(-1) s(-1), about 2 orders of magnitude larger than 0.00614 cm(2 )V(-1) s(-1) of NDI-ID. The present work provides theoretical guidance for the design of ETMs with excellent performance.