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Issue 38, 2014
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Control of charge generation and recombination in ternary polymer/polymer:fullerene photovoltaic blends using amorphous and semi-crystalline copolymers as donors

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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.

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

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Article information


Submitted
01 May 2014
Accepted
16 Jun 2014
First published
17 Jun 2014

Phys. Chem. Chem. Phys., 2014,16, 20329-20337
Article type
Paper

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

H. Mangold, A. A. Bakulin, I. A. Howard, C. Kästner, D. A. M. Egbe, H. Hoppe and F. Laquai, Phys. Chem. Chem. Phys., 2014, 16, 20329
DOI: 10.1039/C4CP01883D

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