Increasing H-aggregation of p-DTS(FBTTh2)2 to improve photovoltaic efficiency by solvent vapor annealing

Zhao, Qingjun; Yu, Xinge; Liu, Jiangang; Xie, Zhiyuan; Han, Yanchun

doi:10.1016/j.orgel.2016.05.044

Cited by 22 publications

(14 citation statements)

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“…The J‐type π–π stacking was beneficial to broaden the photon response region and to facilitate electron transport. [ 13,53 ] The electron mobilities of the C8‐IT‐4F films cast from CF and CB measured by the SCLC method were 1.3 × 10 −3 and 4.7 × 10 −4 cm 2 V −1 s −1 , respectively (Figure S6b and Table S2, Supporting Information), which are consistent with the GIWAXS analysis and the molecular dynamics simulated results of 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐ d :2′,3′‐ d ′]‐s‐indaceno[1,2‐b:5,6‐ b ′]dithiophene amorphous film and crystal. [ 23 ]…”

Section: Resultssupporting

confidence: 76%

Efficient As‐Cast Polymer Solar Cells with High and Stabilized Fill Factor

et al. 2020

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Molecular ordering and miscibility of donor and acceptor materials play critical roles in developing high-performance as-cast polymer solar cells (PSCs). In this work, a highly crystalline nonfullerene small molecular acceptor, namely, C8-IT-4F, based on alkylated indacenodithieno[3,2-b]thiophene as the aromatic core and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile moieties as end groups, is selected and synthesized. The π-π stacking distance in C8-IT-4F film can be tuned from 3.88 Å to a more compact (3.48 Å) state by a film-formation process and the confinement induced by the preaggregated polymer donor PM7, leading to broadened absorption and fine phase separation in the blend film. The optimal morphology with a framework of preaggregated polymer donor, J-type face-on π-π stacked acceptor, and appropriate donor/ acceptor miscibility facilitates charge generation and transport and reduces charge recombination. As a result, the best PSC based on the as-cast PM7:C8-IT-4F blend film exhibits power conversion efficiency of 14.3%, with an open-circuit voltage of 0.82 V, a short-circuit current density of 22.7 mA cm À2 , a fill factor of 77.1%, and good photostability with a stabilized fill factor.

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Section: Resultssupporting

confidence: 76%

Efficient As‐Cast Polymer Solar Cells with High and Stabilized Fill Factor

et al. 2020

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“…Out-of-plane alkyl and in-plane π–π coherence lengths associated with p -DTS(FBTTh 2 ) 2 crystallites in the BHJ films were obtained from Scherrer analysis of the (001)a and (141) peaks, respectively. The peak areas were used to quantify the relative degree of crystallization (crystallite population). , To ensure that variations in scattering intensity were not due to film thickness variations, AFM measurements were performed to confirm that the films had similar thicknesses of 105 ± 8 nm. Figure b–e show the systematic increase in crystallite coherence length and population along the alkyl and π–π stacking directions as φ DTS and DIO concentration are increased.…”

Section: Resultsmentioning

confidence: 99%

In-Plane Pathways Facilitate Out-of-Plane Charge Transport in Organic Solar Cell Active Layers

Mehta

Mativetsky

2018

ACS Appl. Energy Mater.

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Solution-processed organic bulk heterojunctions are promising for enabling low-cost, lightweight, and mechanically flexible solar cells. While the nanostructured interpenetrating donor−acceptor morphology in bulk heterojunctions leads to efficient charge photogeneration, the locally varying composition, crystallinity, and electrical connectivity result in a complex landscape for charge transport. This work examines the structural features that govern out-of-plane charge transport in a highperformance small molecule:fullerene organic photovoltaic system, 7,7-( 42 ) blended with phenyl-C 71 -butyric acid methyl ester (PC 71 BM). Active layer composition and degree of donor− acceptor phase separation were systematically varied and characterized electrically by conductive atomic-force-microscope-based charge carrier mobility mapping and structurally by grazing incidence X-ray diffraction. These experiments reveal that the strongest predictor of out-of-plane hole mobility across all morphologies is the amount of in-plane π−π stacking within the donor phase. Furthermore, as the amount of in-plane π−π stacking increases, the width of moderate-hole-mobility regions concentrated around high-hole-mobility hot spots increases in nanoscale hole-mobility maps, resulting from lateral access of charge from the surrounding regions to the hot spots. These findings challenge the notion that out-of-plane transport in bulk heterojunctions is predominantly dependent on out-of-plane pathways and instead suggests the importance of balancing in-plane and out-of-plane transport components.

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“…PDMS, as a long chain, may enter the aggregation phase of the alkyl side chain of p-DTS(FBTTh 2 ) 2 , due to the similar mutual dissolve theory. The entering of PDMS may increase steric hindrance of the adjacent p-DTS(FBTTh 2 ) 2 molecules resulting in the forming of H-type aggregation, which has a bigger space distance than J-type aggregation, 28 as shown in Scheme 1. So PDMS can improve the H-type aggregation and reduce J-type aggregation; i.e., the ratio of H/J is improved.…”

Section: Resultsmentioning

confidence: 99%

Optimizing H-/J-Type Aggregation and Vertical Phase Separation To Improve Photovoltaic Efficiency of Small Molecule Solar Cells by Adding a Macromolecule Additive

Zhao

Xie

et al. 2018

ACS Appl. Energy Mater.

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Exciton dissociation and charge collection are two key processes for small molecule solar cells. H-type aggregation provides a strong driving force for exciton dissociation due to a higher lowest excited level. Optimal vertical phase separation with the donor and acceptor accumulating on the cathode and anode, respectively, is favorable for charge collection. However, J-type aggregation dominates in 7, 7′-(4,4-bis(2-ethylhexyl)2 ), while p-DTS(FBTTh 2 ) 2 (donor) and [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM, acceptor) tend to accumulate on the cathode and anode, respectively, in the bulk heterojunction (BHJ) solar cell. We proposed to add a macromolecule polydimethylsiloxane (PDMS) into the p-DTS(FBTTh 2 ) 2 /PC 71 BM chlorobenzene (CB) blend solution to enhance both the H-type aggregation and vertical phase separation synchronously. PDMS can enter the aggregation phase of the alkyl side chain of p-DTS(FBTTh 2 ) 2 to increase steric hindrance of the adjacent donor molecules; thus, the ratio of H/J is improved from 0.32 to 0.46. Meanwhile, the network structure PDMS formed impeded PC 71 BM transferring to the bottom of film, with the weight ratio m PC71BM /m p-DTS(FBTTh2)2 improved from 0.036 to 0.159 on the cathode. Both the H-type aggregation and vertical phase separation are propitious to increase efficiency of exciton separation, from 91.6% to 93.9%. As a result, by adding 2% PDMS into the CB solution with 0.2% 1,8-diiodooctane (DIO), the power conversion efficiency (PCE) increased from 6.04% to 6.59%.

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Increasing H-aggregation of p-DTS(FBTTh2)2 to improve photovoltaic efficiency by solvent vapor annealing

Cited by 22 publications

References 42 publications

Efficient As‐Cast Polymer Solar Cells with High and Stabilized Fill Factor

Efficient As‐Cast Polymer Solar Cells with High and Stabilized Fill Factor

In-Plane Pathways Facilitate Out-of-Plane Charge Transport in Organic Solar Cell Active Layers

Optimizing H-/J-Type Aggregation and Vertical Phase Separation To Improve Photovoltaic Efficiency of Small Molecule Solar Cells by Adding a Macromolecule Additive

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