Enhanced Electron Mobility and Interfacial Properties by Introducing Nitrogen and Sulfur Heteroatoms into Naphthalene Diimide-Based Electron Transport Materials for Inverted Perovskite Solar Cells: A Theoretical Study

In perovskite solar cells (PSCs), the electron transportlayer(ETL) plays an important part in the extraction and transport of photogeneratedelectrons in the perovskite layer. Electron transport materials (ETMs)also modify the interface between the perovskite layer and the electrode,reducing charge recombination. In this work, a series of ETMs basedon the experimentally synthesized N,N & PRIME;-bis(1-indanyl) naphthalene-1,4,5,8-tetracarboxylic diimide(NDI-ID) [Kwon, O. P. et al. Adv. Funct. Mater. 2020, 30, 1905951] were designed by introducingthiophene sulfur and pyrrole nitrogen atoms in the N-substituent sidechain. The effects of heteroatom engineering on electronic properties,transfer, and interfacial properties were systematically studied.We found that the designed ETMs have improved the electronic properties.More significantly, compared to the NDI-ID molecule, the electronmobility of the ETMs is significantly increased, even exceeding 26times. Especially, NDI-ID-1S-m exhibits remarkablystronger interfacial interactions with MAPbI(3) and enhancedelectron extraction capability compared with NDI-ID. Our results demonstratethat heteroatom-regulated NDI small molecules are potential ETMs andoffer helpful guidance for the design of durable and efficient componentsfor PSCs.