Jump to main content
Jump to site search

Issue 20, 2017
Previous Article Next Article

Controlling the excited-state energy levels of 9,9′-bifluorenylidene derivatives by twisting their structure to attaining singlet fission character in organic photovoltaics

Author affiliations

Abstract

9,9′-Bifluorenylidene (BFN) derivatives, in which the two fluorene moieties are connected via a C[double bond, length as m-dash]C double bond at the 9-position, are expected to show singlet fission (SF) character in organic photovoltaics (OPVs). Due to steric repulsion between the hydrogen atoms at the 1,8- and 1′,8′-positions, the two fluorene planes of BFN are twisted by 31° with respect to each other. DFT calculations suggest that this deviation from coplanarity lowers the T1 energy level of BFN to approximately half that of S1. We synthesized a molecular alkylbithiophene-substituted BFN and a copolymer of diketopyrrolopyrrole and BFN. The optoelectronic properties of these compounds were investigated, and OPV devices using these BFNs as a p-type material were fabricated. The device composed of the polymeric BFN derivative achieved a power conversion efficiency of 4.9%. The observed negative dependence of the photocurrent on the magnetic field suggested that the triplet excitons of the molecular BFN derivatives contribute to the photocurrent in these OPV devices.

Graphical abstract: Controlling the excited-state energy levels of 9,9′-bifluorenylidene derivatives by twisting their structure to attaining singlet fission character in organic photovoltaics

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 19 Jan 2017, accepted on 26 Apr 2017 and first published on 26 Apr 2017


Article type: Paper
DOI: 10.1039/C7TC00315C
Citation: J. Mater. Chem. C, 2017,5, 4909-4914
  •   Request permissions

    Controlling the excited-state energy levels of 9,9′-bifluorenylidene derivatives by twisting their structure to attaining singlet fission character in organic photovoltaics

    S. Kawata, J. Furudate, T. Kimura, H. Minaki, A. Saito, H. Katagiri and Y. Pu, J. Mater. Chem. C, 2017, 5, 4909
    DOI: 10.1039/C7TC00315C

Search articles by author