Molecular packing of non-fullerene acceptors for organic solar cells: Distinctive local morphology in Y6 vs. ITIC derivatives

G. Kupgan, X.K. Chen, J.L. Brédas

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

75 Citations (Scopus)
152 Downloads (CityUHK Scholars)

Abstract

Since a couple of years ago, Y6 has emerged as one of the main non-fullerene acceptors for organic solar cells, as its use leads to superior power conversion efficiencies. It is thus of major interest to investigate the multiscale phenomena that are responsible for Y6's efficacy. Here, we modeled neat films of Y6 and earlier non-fullerene acceptors, IT-4F and ITIC, using a combination of density functional theory calculations and molecular dynamics simulations, to investigate the various factors that control their charge and exciton transport rates. We find that the molecular packing in Y6 is drastically different from that in IT-4F and ITIC. At the nanoscale, the local morphology of Y6 consists of a large number of directional face-on stackings and well-connected transport networks. Y6 also consistently shows higher electronic couplings for LUMOs, HOMOs, and local excitations than ITIC-type acceptors, which results in fast transport rates for electrons, holes, and excitons. Importantly, when considering dimers, their configurations in Y6 are more diverse than in ITIC-type acceptors, with many of those similar to the configurations observed in the Y6 crystal structure reported recently. Most Y6 dimer configurations exhibit strong binding interactions, large electronic couplings, and high transport rates, which when taken together rationalize the better performance of OSCs based on Y6.
Original languageEnglish
Article number100154
JournalMaterials Today Advances
Volume11
Online published18 Jul 2021
DOIs
Publication statusPublished - Sept 2021
Externally publishedYes

Research Keywords

  • Density functional theory
  • Electronic couplings
  • Molecular dynamics
  • Packing configurations
  • Transport rates

Publisher's Copyright Statement

  • This full text is made available under CC-BY-NC-ND 4.0. https://creativecommons.org/licenses/by-nc-nd/4.0/

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