Charge Generation and Recombination in Diketopyrrolopyrrole Polymer: Fullerene Bulk Heterojunctions Studied by Transient Absorption and Time-Resolved Microwave Conductivity

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Author(s)
Katoh, Ryuzi
Matsuzaki, Hiroyuki
Furube, Akihiro
Sonar, Prashant
Williams, Evan L
Vijila, Chellappan
Subramanian, Gomathy Sandhya
Gorelik, Sergey
Hobley, Jonathan
Griffith University Author(s)
Year published
2016
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Charge generation and recombination dynamics in organic photovoltaic bulk heterojunction films comprising the donor polymer, PDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene}), blended with the fullerene acceptor, PC71BM ([6,6]-phenyl C71-butyric acid methyl ester), have been studied. The charge-carrier generation process was studied using femtosecond transient absorption, and it was found that the efficiency of charge generation is not dominated by geminate recombination but rather is limited by exciton diffusion in the films. Highly sensitive nanosecond transient ...
View more >Charge generation and recombination dynamics in organic photovoltaic bulk heterojunction films comprising the donor polymer, PDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene}), blended with the fullerene acceptor, PC71BM ([6,6]-phenyl C71-butyric acid methyl ester), have been studied. The charge-carrier generation process was studied using femtosecond transient absorption, and it was found that the efficiency of charge generation is not dominated by geminate recombination but rather is limited by exciton diffusion in the films. Highly sensitive nanosecond transient absorption (ns-TA) and time-resolved microwave conductivity (TRMC) were used to study charge recombination. From ns-TA measurements, we obtained a recombination rate constant of 1 × 10–9 cm3 s–1 and found that charge recombination is limited by the diffusion of charge carriers (Langevin-type recombination). TRMC signals were comparable with ns-TA on shorter time scales. However, in contrast with ns-TA, the TRMC signal contained an additional long-lived component. The fast decay on shorter time scales is attributed to the recombination of the majority of the charge carriers. The long-lived component is assigned to a small population of charge carriers with high mobility, suggesting they are located in isolated, crystalline domains within the bulk heterojunction. These findings are discussed in relation to the morphology of the blend film, fluorescence quenching properties, and device performance including photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) measurements described in our previous publications.
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View more >Charge generation and recombination dynamics in organic photovoltaic bulk heterojunction films comprising the donor polymer, PDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene}), blended with the fullerene acceptor, PC71BM ([6,6]-phenyl C71-butyric acid methyl ester), have been studied. The charge-carrier generation process was studied using femtosecond transient absorption, and it was found that the efficiency of charge generation is not dominated by geminate recombination but rather is limited by exciton diffusion in the films. Highly sensitive nanosecond transient absorption (ns-TA) and time-resolved microwave conductivity (TRMC) were used to study charge recombination. From ns-TA measurements, we obtained a recombination rate constant of 1 × 10–9 cm3 s–1 and found that charge recombination is limited by the diffusion of charge carriers (Langevin-type recombination). TRMC signals were comparable with ns-TA on shorter time scales. However, in contrast with ns-TA, the TRMC signal contained an additional long-lived component. The fast decay on shorter time scales is attributed to the recombination of the majority of the charge carriers. The long-lived component is assigned to a small population of charge carriers with high mobility, suggesting they are located in isolated, crystalline domains within the bulk heterojunction. These findings are discussed in relation to the morphology of the blend film, fluorescence quenching properties, and device performance including photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) measurements described in our previous publications.
View less >
Journal Title
Journal of Physical Chemistry C
Volume
120
Issue
50
Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright 2016 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcc.6b08379
Subject
Chemical sciences
Engineering
Science & Technology
Physical Sciences
Chemistry, Physical
Nanoscience & Nanotechnology