Issue 42, 2018

The effect of side-chain substitution on the aggregation and photovoltaic performance of diketopyrrolopyrrole-alt-dicarboxylic ester bithiophene polymers

Abstract

Using a dicarboxylic ester bithiophene (DCBT) co-monomer, electron-withdrawing ester groups are introduced on the two central thiophene rings of an alternating donor–acceptor polymer (PDPP4T) consisting of diketopyrrolopyrrole (DPP) and quaterthiophene (4T) to increase the oxidation potential and reduce the photon energy loss in solar cells. To counteract the increased solubility of the PDPPDCBT polymers owing to the ester side chains, linear instead of branched side chains were used on the DPP monomer. The length of the ester side chains was varied to study their effect on the optoelectronic properties, morphology and photovoltaic performance of these polymers in bulk-heterojunction blends with PC71BM as acceptor. The molecular weight of PDPPDCBT is limited, because the bisstannyl-DPP monomer could not be completely purified from mono-functional analogues. By using a non-stoichiometric monomer ratio or a branching unit, the molecular weights were improved to ∼35 kDa. A maximum power conversion efficiency of PCE = 5.7% was obtained. Compared to the parent PDPP4T (PCE 7.0%), the photon energy loss for the best PDPPDCBT was reduced from 0.79 to 0.76 eV, but the photon-to-electron quantum efficiency was reduced, as a consequence of a too coarse phase separation, as studied with two-dimensional grazing-incidence X-ray scattering and transmission electron microscopy.

Graphical abstract: The effect of side-chain substitution on the aggregation and photovoltaic performance of diketopyrrolopyrrole-alt-dicarboxylic ester bithiophene polymers

Supplementary files

Article information

Article type
Paper
Submitted
03 Jun 2018
Accepted
15 Aug 2018
First published
17 Oct 2018
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. A, 2018,6, 20904-20915

The effect of side-chain substitution on the aggregation and photovoltaic performance of diketopyrrolopyrrole-alt-dicarboxylic ester bithiophene polymers

R. Heuvel, F. J. M. Colberts, J. Li, M. M. Wienk and R. A. J. Janssen, J. Mater. Chem. A, 2018, 6, 20904 DOI: 10.1039/C8TA05238G

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements