Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide–thienoacene dimers

Ariel A. Leonard; Martín A. Mosquera; Leighton O. Jones; Zhengxu Cai; Thomas J. Fauvell; Matthew S. Kirschner; David J. Gosztola; George C. Schatz; Richard D. Schaller; Luping Yu; Lin X. Chen

doi:10.1039/D0SC02862B

Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide–thienoacene dimers†

Ariel A. Leonard,

^a Martín A. Mosquera,

^a Leighton O. Jones,

^a Zhengxu Cai,

^b Thomas J. Fauvell,^a Matthew S. Kirschner,^a David J. Gosztola,

^d George C. Schatz,

*^a Richard D. Schaller,*^ad Luping Yu*^c and Lin X. Chen

*^ae

Author affiliations

* Corresponding authors

^a Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
E-mail: l-chen@northwestern.edu

^b Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China

^c Department of Chemistry and James Frank Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA

^d Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue Lemont, Illinois 60439, USA

^e Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, USA
E-mail: lchen@anl.gov

Abstract

Perylenediimide (PDI) derivatives have been widely studied as electron acceptor alternatives to fullerenes in organic photovoltaics (OPVs) because of their tunable absorption in the visible range, inexpensive synthesis, and photochemical stability. A common motif for improving device efficiency involves joining multiple PDIs together through electron-rich linkers to form a twisted acceptor–donor–acceptor molecule. Molecular features such as ring fusion are further employed to modify the structure locally and in films. These synthetic efforts have greatly enhanced OPV device efficiencies, however it remains unclear how the increasingly elaborate structural modifications affect the photophysical processes integral to efficient photon-to-charge conversion. Here we carry out a systematic study of a series of PDI dimers with thienoacene linkers in which the twist angle, linker length, and degree of ring fusion are varied to investigate the effects of these structural features on the molecular excited states and exciton recombination dynamics. Spectroscopic characterization of the dimers suggest that ring fusion causes greater coupling between the donor and acceptor components and greatly enhances the lifetime of a thienoacene to PDI charge transfer state. The lifetime of this CT state also correlates well with the linker–PDI dihedral angle, with smaller dihedral angle resulting in longer lifetime. DFT and two-photon absorption TDDFT calculations were developed in-house to model the ground state and excited transitions, providing theoretical insight into the reasons for the observed photophysical properties and identifying the charge transfer state in the excited state absorption spectra. These results highlight how the longevity of the excited state species, important for the efficient conversion of excitons to free carriers in OPV devices, can be chemically tuned by controlling ring fusion and by using steric effects to control the relative orientations of the molecular fragments. The results provide a successful rationalization of the behavior of solar cells involving these acceptor molecules.

This article is part of the themed collection: Papers celebrating the birthday and achievements of Professor Michael Wasielewski

Chemical Science

Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide–thienoacene dimers†

Abstract

Supplementary files

Article information

Download Citation

Permissions

Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide–thienoacene dimers

Social activity

Search articles by author

Spotlight

Advertisements