Charge-transfer (CT) states formed at organic donor-acceptor (D-A) semiconductor heterojunctions play a critical role in optoelectronic devices. While mobile, their migration has not been extensively characterized. In addition, the factors impacting the CT state diffusion length (LD) have not been elucidated. Here, CT state LD is measured by using photoluminescence quenching for several D-A mixtures, with migration occurring along the bulk heterojunction. All D-A pairings considered yield a similar LD ∼ 5 nm in equal mixtures despite variations in the CT state energy and the constituent molecular structures. The CT state LD varies strongly with mixture composition and is well-correlated to the slowest charge carrier mobility, suggesting a direct method to tune CT state transport. These findings may be applied to elucidate the role of CT state migration in organic photovoltaic and light-emitting devices as well as to broadly explain the transport of interfacial excited states along inorganic and hybrid organic-inorganic heterojunctions.
Bibliographical noteFunding Information:
This work was supported by National Science Foundation (NSF) Electronics, Photonics and Magnetic Devices under ECCS-1509121 and Solid-State and Materials Chemistry under DMR-1708177. T.Z. acknowledges support through a University of Minnesota Doctoral Dissertation Fellowship. N.M.C. acknowledges support from the NSF Graduate Research Fellowship under Grant 00074041. R.J.H. acknowledges support from Ronald L. and Janet A. Christenson, a Leverhulme Trust Visiting Professorship at the University of Cambridge, and a Visiting Fellowship at Clare Hall, University of Cambridge. Parts of this work were performed in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program.
- Charge-transfer state
- Donor-acceptor heterojunction
- Energy transfer
- Exciton diffusion
- Exciton transport
- Organic semiconductor
PubMed: MeSH publication types
- Journal Article