Control of charge generation and recombination in ternary polymer/polymer: fullerene photovoltaic blends using amorphous and semi-crystalline copolymers as donors

Hannah Mangold, Artem A. Bakulin, Ian A. Howard, Christian Kästner, Daniel A M Egbe, Harald Hoppe*, Frédéric Laquai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Charge generation and recombination processes occurring in ternary photoactive copolymer:copolymer:fullerene blends consisting of different mixing ratios between entirely amorphous and semi-crystalline PPE-PPV copolymers are investigated by transient absorption pump-probe and pump-push photocurrent spectroscopy. The experiments reveal that an excess of semi-crystalline polymer facilitates exciton dissociation into free charge carriers, slows down geminate recombination, and suppresses non-geminate recombination leading to increased short-circuit currents and high fill factors. In contrast, blends utilizing solely the amorphous polymer for their donor phase suffer from a large fraction of sub-nanosecond geminate recombination of interfacially bound charge-transfer states and also from fast non-geminate recombination of free charges, resulting in a significantly reduced photovoltaic performance. However, small fractions of the amorphous polymer blended into the semi-crystalline polymer increase the open-circuit voltage and the fill factor, while keeping the charge generation and recombination parameters largely unaltered in turn leading to an optimized device performance for the ternary PPE-PPV copolymer:copolymer:fullerene blends.

Original languageEnglish (US)
Pages (from-to)20329-20337
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number38
DOIs
StatePublished - Oct 14 2014
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

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