Rational Design of Small Molecular Donor for Solution‐Processed Organic Photovoltaics with 8.1% Efficiency and High Fill Factor via Multiple Fluorine Substituents and Thiophene Bridge

Wang, Jinliang; Yin, Qing-Ru; Miao, Jingsheng; Wu, Zhuo; Chang, Zhengfeng; Cao, Yue; Zhang, Rubo; Wang, Jieyu; Wu, Hongbin; Cao, Yong

doi:10.1002/adfm.201500190

Cited by 114 publications

(62 citation statements)

References 85 publications

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“…It was very challenging to synthesize the targeted molecules with high effi ciency due to the lack of regioselectivity of the two bromide reaction sites of the difl uorinated benzothiadiazole, which led to a low isolated yield of the mono-functionalized difl uorinated benzothiadiazole. BIT4FFu was obtained through Stille coupling reactions between 3 and the monobromide intermediate 4 [ 85 ] in 87% isolated yield. 5 was obtained by wileyonlinelibrary.coma Stille coupling reaction between 4 and 2-tributyltinthiophene in 93% isolated yield.…”

Section: Resultsmentioning

confidence: 99%

Difluorobenzothiadiazole‐Based Small‐Molecule Organic Solar Cells with 8.7% Efficiency by Tuning of π‐Conjugated Spacers and Solvent Vapor Annealing

Wang

Xiao

Yan

et al. 2016

Adv Funct Materials

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101

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The synthesis of a series of tetrafl uorine-substituted, wide-bandgap, small molecules consisting of various π-conjugated spacers (furan, thiophene, selenophene) between indacenodithiophene as the electron-donating core and the electron-defi cient difl uorobenzothiadiazole unit is reported and the effect of the π-conjugated spacers on the photovoltaic properties is investigated. The alteration of the π-conjugated spacer enables fi ne-tuning of the photophysical properties and energy levels of the small molecules, and allows the adjustment of the charge-transport properties, the morphology of the photoactive fi lms, as well as their photovoltaic properties. Moreover, most of these devices exhibit superior device performances after CH 2 Cl 2 solvent annealing than without annealing, with a high fi ll factor (0.70-0.75 for all cases). Notably, the devices based on the new molecule BIT4FTh (with thiophene as the spacer) show an outstanding PCE of 8.7% (with an impressive FF of 0.75), considering its wide-bandgap (1.81 eV), which is among the highest effi ciencies reported so far for small-molecules-based solar cells. The morphologies of the photoactive layers with/without CH 2 Cl 2 solvent annealing are characterized by atomic force microscopy, transmission electron microscopy and two-dimensional grazing incidence X-ray diffraction analysis. The results reported here clearly indicate that highly effi cient small-molecules-based solar cells can be achieved through rational design of their molecular structure and optimization of the phaseseparated morphology via an adapted solvent-vapor annealing process.

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Section: Resultsmentioning

confidence: 99%

Difluorobenzothiadiazole‐Based Small‐Molecule Organic Solar Cells with 8.7% Efficiency by Tuning of π‐Conjugated Spacers and Solvent Vapor Annealing

Wang

Xiao

Yan

et al. 2016

Adv Funct Materials

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101

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“…The effects of thiophene π-bridge and multiple-fluorinated modules on the photovoltaic properties were investigated by Cao's group [32]. Very recently, they showed three molecule 6a-c, by incorporating multiple fluorine substituents of benzothiadiazole and inserting thiophene spacers, the PV performance is dramatically improved.…”

Section: Thiophene-linkagementioning

confidence: 99%

π-Linkage effect of push-pull-structure organic small molecules for photovoltaic application

Yin

2016

Sci. China Mater.

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Much attention has been paid to the push-pullstructure organic small molecule (OSM) materials for photovoltaic (PV) application in the past decade, due to their facile reduction of energy band gap (Eg) and effective control of PV properties. π-bridge plays an important role in the push-pull-structure OSMs since an appropriate π-linkage is crucial for improving the PV performance of organic solar cells (OSCs). In this review, various π-bridge groups (thiophene, alkene, alkyne, arene and heterocycle) and the pertinent π-linkage effect will be systematically summarized. These results suggest that the in-depth study of the π-linkage effect is essential to deeply understanding the relationship between the molecular structure and property, thus improving PV performance.

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“…The thin-film UV-vis absorption spectra of SM1-3 are superimposed in Figure 1a, and the solution (in CHCl3) and thin-film spectra for each SM system are overlaid in Figure S1a 25,[54][55] The absence of long-wavelength absorption shoulders in the solution spectra of SM1-3 indicates that the molecules are not subject to π-aggregation at the concentration of this experiment (1x10 -5 M). In thin films (Fig.…”

Section: Design Synthesis and Materials Propertiesmentioning

confidence: 99%

Solvent Annealing Effects in Dithieno[3,2-b:2′,3′-d]pyrrole–5,6-Difluorobenzo[c][1,2,5]thiadiazole Small Molecule Donors for Bulk-Heterojunction Solar Cells

et al. 2016

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Low-bandgap small molecule (SM) donors that can be solution-processed with fullerene acceptors (e.g. PC61/71BM) are proving particularly promising in bulk-heterojunction (BHJ) solar cells. Compared to their π-conjugated polymer counterparts, SM donors are well defined (monodispersed) and more synthetically modular -with relatively wide ranges of bandgaps achievable in stepwise couplings of various donor and acceptor motifs. However, the optimization of SM-fullerene morphologies and BHJ device efficiencies relies more specifically on the use of processing additives, post-processing thermal or solvent vapor annealing (SVA) approaches, and achieving adequate interpenetrating networks and structural order in BHJ thin films can be challenging. In this report, we examine the correlated effects of molecular structure and post-processing SVA on the BHJ solar cell performance of a set of π-extended SM donors composed of dithieno[3,2-b:2',3'-d]pyrrole (DTP) and 5,6-difluorobenzo[c][1,2,5]thiadiazole ([2F]BT) units. In these systems (SM1-3), the introduction of additional alkyl substituents and unsubstituted thiophene rings on the peripheral unit groups critically impacts the effects of SVA steps on BHJ solar cell efficiency. We show that the more π-extended and alkyl-substituted analogue SM3 stands out -with BHJ device efficiencies of ca. 6% obtained from SVA with CS2-while SVA-treated SM3-based active layers also show the most favorable ordering and carrier mobility patterns. However, unlike numbers of SM donors reported in recent years, DTP-[2F]BT SM analogues are in general not prone to dramatic performance variations in BHJ thin films cast with processing additives. Our results indicate that the role of SVA steps is not independent of the molecular structure of the SM donors used in the BHJ solar cells.

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Rational Design of Small Molecular Donor for Solution‐Processed Organic Photovoltaics with 8.1% Efficiency and High Fill Factor via Multiple Fluorine Substituents and Thiophene Bridge

Cited by 114 publications

References 85 publications

Difluorobenzothiadiazole‐Based Small‐Molecule Organic Solar Cells with 8.7% Efficiency by Tuning of π‐Conjugated Spacers and Solvent Vapor Annealing

Difluorobenzothiadiazole‐Based Small‐Molecule Organic Solar Cells with 8.7% Efficiency by Tuning of π‐Conjugated Spacers and Solvent Vapor Annealing

π-Linkage effect of push-pull-structure organic small molecules for photovoltaic application

Solvent Annealing Effects in Dithieno[3,2-b:2′,3′-d]pyrrole–5,6-Difluorobenzo[c][1,2,5]thiadiazole Small Molecule Donors for Bulk-Heterojunction Solar Cells

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