Domain Compositions and Fullerene Aggregation Govern Charge Photogeneration in Polymer/Fullerene Solar Cells

Kesava, Sameer Vajjala; Fei, Zhuping; Rimshaw, Adam; Wang, Cheng; Hexemer, Alexander; Asbury, John B.; Heeney, Martin; Gomez, Enrique D.

doi:10.1002/aenm.201400116

Cited by 81 publications

(91 citation statements)

References 73 publications

(180 reference statements)

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“…This could possibly be explained due to better exciton dissociation or reduced charge recombination resulted from the phase separation between polymer and PC 71 BM. 64 When a higher post-annealing temperature (i.e. 160 °C) was applied to the device, a decline in the mean value of J SC was observed as well as V OC compared to the device performance without post-annealing.…”

Section: 61mentioning

confidence: 96%

Environmentally friendly preparation of nanoparticles for organic photovoltaics

Pan

Sharma

Gedefaw

et al. 2018

Organic Electronics

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Aqueous nanoparticle dispersions were prepared from a conjugated polymer poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3',2'-h][1,5]naphthyridine-5,10-dione) (PTNT) and fullerene blend utilizing chloroform as well as a non-chlorinated and environmentally benign solvent, o-xylene, as the miniemulsion dispersed phase solvent. The nanoparticles (NPs) in the solid-state film were found to coalesce and offered a smooth surface topography upon thermal annealing. Organic photovoltaics (OPVs) with photoactive layer processed from the nanoparticle dispersions prepared using chloroform as the miniemulsion dispersed phase solvent were found to have a power conversion efficiency M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT2 (PCE) of 1.04%, which increased to 1.65% for devices utilizing NPs prepared from o-xylene.Physical, thermal and optical properties of NPs prepared using both chloroform and o-xylene were systematically studied using dynamic mechanical thermal analysis (DMTA) and photoluminescence (PL) spectroscopy and correlated to their photovoltaic properties. The PL results indicate different morphology of NPs in the solid state were achieved by varying miniemulsion dispersed phase solvent.

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Section: 61mentioning

confidence: 96%

Environmentally friendly preparation of nanoparticles for organic photovoltaics

Pan

Sharma

Gedefaw

et al. 2018

Organic Electronics

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“…[ 30,69 ] Following recently established procedures [ 24 ] a simple analysis using the Scherrer equation [ 70 ] of the peak reveals the coherence length within the PC 71 BM aggregates. The PC 71 BM coherence length for the annealed samples with respect to annealing temperature is shown in the inset of Figure 3 b.…”

Section: Molecular Ordering Domain Size and Composition Variationmentioning

confidence: 99%

“…[ 28 ] Although the power conversion effi ciency (PCE) of organic BHJ solar cells continues to increase, there has been a growing interest in quantifying the mechanisms and morphology that affect device performance. [29][30][31][32][33][34] Given that many factors infl uence the photovoltaic performance of BHJ devices via charge generation and extraction, it has often been very diffi cult to deduce explicit correlations between a change in morphology and an observed variation in device performance, let alone offer straightforward yet convincing physical causes. Hence, a deeper understanding of these processes may enable the design of materials that are more effi cient and would aid future commercialization efforts.…”

mentioning

confidence: 99%

Significance of Average Domain Purity and Mixed Domains on the Photovoltaic Performance of High‐Efficiency Solution‐Processed Small‐Molecule BHJ Solar Cells

Mukherjee

Proctor

Bazan

et al. 2015

Advanced Energy Materials

138

166

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the donor-acceptor ratio, [7][8][9] the molecular weight, [10][11][12][13] side-chain engineering, [14][15][16] choice of solvent, [17][18][19] fl uorine substitution, [ 20 ] solvent mixtures, [ 21 ] additives, [ 22,23 ] solvent, [ 21,[24][25][26][27] and thermal annealing. [ 28 ] Although the power conversion effi ciency (PCE) of organic BHJ solar cells continues to increase, there has been a growing interest in quantifying the mechanisms and morphology that affect device performance. [29][30][31][32][33][34] Given that many factors infl uence the photovoltaic performance of BHJ devices via charge generation and extraction, it has often been very diffi cult to deduce explicit correlations between a change in morphology and an observed variation in device performance, let alone offer straightforward yet convincing physical causes. Hence, a deeper understanding of these processes may enable the design of materials that are more effi cient and would aid future commercialization efforts.For most BHJ systems, improved solar cell performance has been achieved by varying the fi lm processing conditions often leading to a distinctly different morphology from those seen in lower performing devices. This has led to the model and expectation that pure domains with lateral in-plane dimensions of ≈10 nm need to be matched with the exciton diffusion length alongside high electron as well as hole mobilities. [ 20,35 ] It has also been shown that in bilayer model systems with single planar heterojunctions as well as in polymer-fullerene BHJs the degree of preferential molecular orientation relative to donor-acceptor interface is strongly correlated with the shortcircuit current ( J sc ) and fi ll factor ( FF ). [36][37][38] More recently, it was reported that the miscibility of the fullerene in the donor can be considerable and the mixed component domains lead to excellent exciton quenching and charge generation. [38][39][40][41][42][43][44][45][46][47] The actual morphologies might thus comprise three phases, with relatively pure, aggregated donor and acceptor domains in addition to mixed amorphous regions, as shown in Figure 1 . It has been suggested that indeed this three phase morphology may be favorable as the electronic structure of both the donor and acceptor depends on the level of aggregation, thus providing an electronic landscape that can help to sweep charges out of the mixed domains. [ 33,[48][49][50] Recent studies on polymer:fullerene systems reveal that average domain purity of the mixed phase

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“…[ 14 ] As an electron-rich comonomer, we investigated dithienogermole (DTG) due to the promising performance of the PDTG-TPD copolymer previously reported, and our experience with this comonomer. [ 15 ] We fi nd that the incorporation of small amounts (20%) of cross-linkable monomer has a benefi cial impact on overall device effi ciency before cross-linking. The role of various processing additives is investigated, and we fi nd that the use of 1,8-diiodoctane (DIO) causes unexpected stability issues when the fi lms are irradiated with UV radiation.…”

Section: Introductionmentioning

confidence: 98%

Investigation of Radical and Cationic Cross‐Linking in High‐Efficiency, Low Band Gap Solar Cell Polymers

Yau

Wang

Treat

et al. 2014

Advanced Energy Materials

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Dithienogermole‐co‐thieno[3,4‐c]pyrroledione (DTG‐TPD) polymers incorporating chemically cross‐linkable sidechains are reported and their properties compared to a parent polymer with simple octyl sidechains. Two cross‐linking groups and mechanisms are investigated, UV‐promoted radical cross‐linking of an alkyl bromide cross‐linker and acid‐promoted cationic cross‐linking of an oxetane cross‐linker. It is found that random copolymers with a 20% incorporation of the cross‐linker demonstrate a higher performance in bulk heterojunction solar cells than the parent polymer, while 100% cross‐linker incorporation results in deterioration in device efficiency. The use of 1,8‐diiodooctane (DIO) as a processing additive improves as‐cast solar cell performance, but is found to have a significant deleterious impact on solar cell efficiency after UV exposure. The instability to UV can be overcome by the use of an alternative additive, 1‐chloronapthalene, which also promotes high device efficiency. Cross‐linking of the polymer is investigated in the presence and absence of fullerene highlighting significant differences in behavior. Intractable films cannot be obtained by radical cross‐linking in the presence of fullerene, whereas cationic cross‐linking is successful.

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Domain Compositions and Fullerene Aggregation Govern Charge Photogeneration in Polymer/Fullerene Solar Cells

Cited by 81 publications

References 73 publications

Environmentally friendly preparation of nanoparticles for organic photovoltaics

Environmentally friendly preparation of nanoparticles for organic photovoltaics

Significance of Average Domain Purity and Mixed Domains on the Photovoltaic Performance of High‐Efficiency Solution‐Processed Small‐Molecule BHJ Solar Cells

Investigation of Radical and Cationic Cross‐Linking in High‐Efficiency, Low Band Gap Solar Cell Polymers

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