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Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification.

ABSTRACT: The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. We also find that fullerene preferentially mixes into disordered regions of the polymer film. This shows that relatively small differences in molecular structure are important for exciton diffusion and fullerene distribution.

SUBMITTER: Sajjad MT

PROVIDER: S-EPMC4565514 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification.

Sajjad Muhammad T MT Ward Alexander J AJ Kästner Christian C Ruseckas Arvydas A Hoppe Harald H Samuel Ifor D W ID

The journal of physical chemistry letters 20150722 15

The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. We also find that fullerene preferentially mixes into disordered regions of the polymer film. This show ...[more]

PMID: 26267202

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Project description:We study the effects of patterned surface chemistry on the microscale and nanoscale morphology of solution-processed donor/acceptor polymer-blend films. Focusing on combinations of interest in polymer solar cells, we demonstrate that patterned surface chemistry can be used to tailor the film morphology of blends of semiconducting polymers such as poly-[2-(3,7-dimethyloctyloxy)-5-methoxy-p-phenylenevinylene] (MDMO-PPV), poly-3-hexylthiophene (P3HT), poly[(9,9-dioctylflorenyl-2,7-diyl)-co-benzothiadiazole)] (F8BT), and poly(9,9-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylendiamine) (PFB) with the fullerene derivative, [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM). We present a method for generating patterned, fullerene-terminated monolayers on gold surfaces and use microcontact printing and Dip-Pen Nanolithography (DPN) to pattern alkanethiols with both micro- and nanoscale features. After patterning with fullerenes and other functional groups, we backfill the rest of the surface with a variety of thiols to prepare substrates with periodic variations in surface chemistry. Spin coating polymer:PCBM films onto these substrates, followed by thermal annealing under nitrogen, leads to the formation of structured polymer films. We characterize these films with Atomic Force Microscopy (AFM), Raman spectroscopy, and fluorescence microscopy. The surface patterns are effective in guiding phase separation in all of the polymer:PCBM systems investigated and lead to a rich variety of film morphologies that are inaccessible with unpatterned substrates. We demonstrate our ability to guide pattern formation in films thick enough to be of interest for actual device applications (up to 200 nm in thickness) using feature sizes as small as 100 nm. Finally, we show that the surface chemistry can lead to variations in film morphology on length scales significantly smaller than those used in generating the original surface patterns. The variety of behaviors observed and the wide range of control over polymer morphology achieved at a variety of different length scales have important implications for the development of bulk heterojunction solar cells.

Dataset Information

Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification.

Publications

Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification.

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