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Structural Dynamics of Polymer:Non-Fullerene Organic Solar Cell Blends: A Neutron Spectroscopy Perspective

Zbiri, M; Gilhooly-Finn, PA; Fouquet, P; Nielsen, CB; Guilbert, AAY; (2022) Structural Dynamics of Polymer:Non-Fullerene Organic Solar Cell Blends: A Neutron Spectroscopy Perspective. Chemistry of Materials , 34 (17) pp. 7937-7946. 10.1021/acs.chemmater.2c01705. Green open access

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Abstract

Organic solar cells (OSCs) based on ADA-type (acceptor–donor–acceptor) non-fullerene acceptors (NFAs) exhibit improved power conversion efficiency (PCE) compared to the conventional fullerene-based analogues. The optoelectronic properties of the OSC active layer are correlated to the underlying structural dynamics of the active layer blend and therefore influence the device performance. Using synergistically different neutron spectroscopy techniques, we studied the dynamics of binary and ternary blends made of the non-fullerene acceptors O-IDTBR and O-IDFBR and the regioregular donor polymer poly(3-hexylthiophene) (P3HT). Considering key factors like structural relaxation, miscibility, and morphology, within a chosen temperature range, we probed the dynamical responses of the neat phases and the blends using time-of flight quasi-elastic neutron scattering and neutron spin echo measurements, complemented by neutron vibrational spectroscopy. We cover the femtosecond to nanosecond time window directly relevant to the operating active layer molecular processes. Blends of protonated O-IDTBR and O-IDFBR with either deuterated or protonated P3HT were considered for a contrast variation purpose. Our study confirms the observation of the hypomiscibilty of O-IDTBR in the binary P3HT:O-IDTBR compared to O-IDFBR in P3HT:O-IDFBR and points toward a molecular alloying character of the NFA blend O-IDTBR:O-IDFBR, not observed in the ternary P3HT:O-IDTBR:O-IDFBR. A main outcome of this work is the evidenced similar dynamical response of the donor and acceptor components in both the binary and ternary blends, within the accessible experimental picosecond–nanosecond time window and up to 400 K. This finding is in contrast with our previous neutron spectroscopy and molecular dynamics studies of the fullerene-based blend P3HT:PCBM (PCBM: phenyl-C61-butyric acid methyl ester), where we highlighted distinct behaviors of P3HT and PCBM in the blend in terms of the vitrification/frustration of P3HT upon blending and the plasticization of PCBM by P3HT. Alike P3HT vitrification is not presently observed, which we ascribe to the resemblance of the chemical structures of O-IDTBR/O-IDFBR and P3HT. The absence or the weak vitrification evidenced here is in line with recent reports and is likely related to the improved PCE exhibited by the ADA-type NFA-based OSCs.

Type: Article
Title: Structural Dynamics of Polymer:Non-Fullerene Organic Solar Cell Blends: A Neutron Spectroscopy Perspective
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.chemmater.2c01705
Publisher version: https://doi.org/10.1021/acs.chemmater.2c01705
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Miscibility, Neutron scattering, Organic electronics, Solar cells, Structural dynamics
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10190618
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