Recent advances in water/alcohol-soluble π-conjugated materials: new materials and growing applications in solar cells

Duan, Chunhui; Zhang, Kai; Zhong, Chengmei; Huang, Fei; Cao, Yong

doi:10.1039/c3cs60200a

Cited by 450 publications

(366 citation statements)

References 255 publications

(337 reference statements)

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“…When annealed at 150 °C, FF was improved to 71.80%; however V oc and J sc both decreased, reducing the PCE to 8.06%. Further optimization of device performance was carried out by using a conjugated polyelectrolyte interfacial layer of poly[(9,9‐bis(3‐( N , N ‐dimethyl)‐ N ‐ethylammonium)‐propyl)‐2,7‐fluorene)‐ alt ‐2,7‐(9,9‐dioctylfluorene)]dibromide (PFN‐Br) for the 120 °C annealing condition 19. It was seen that FF of the device increased to 73.95% and a PCE of 8.63% was obtained.…”

Section: Resultsmentioning

confidence: 99%

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

Lan

Chen

et al. 2016

Advanced Science

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A novel donor–acceptor type conjugated polymer based on a building block of 4,8‐di(thien‐2‐yl)‐6‐octyl‐2‐octyl‐5H‐pyrrolo[3,4‐f]benzotriazole‐5,7(6H)‐dione (TZBI) as the acceptor unit and 4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene as the donor unit, named as PTZBIBDT, is developed and used as an electron‐donating material in bulk‐heterojunction polymer solar cells. The resulting copolymer exhibits a wide bandgap of 1.81 eV along with relatively deep highest occupied molecular orbital energy level of −5.34 eV. Based on the optimized processing conditions, including thermal annealing, and the use of a water/alcohol cathode interlayer, the single‐junction polymer solar cell based on PTZBIBDT:PC71BM ([6,6]‐phenyl‐C71‐butyric acid methyl ester) blend film affords a power conversion efficiency of 8.63% with an open‐circuit voltage of 0.87 V, a short circuit current of 13.50 mA cm−2, and a fill factor of 73.95%, which is among the highest values reported for wide‐bandgap polymers‐based single‐junction organic solar cells. The morphology studies on the PTZBIBDT:PC71BM blend film indicate that a fibrillar network can be formed and the extent of phase separation can be manipulated by thermal annealing. These results indicate that the TZBI unit is a very promising building block for the synthesis of wide‐bandgap polymers for high‐performance single‐junction and tandem (or multijunction) organic solar cells.

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Section: Resultsmentioning

confidence: 99%

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

Lan

Chen

et al. 2016

Advanced Science

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“…By anchoring the EC interlayer material on the ITO surface, an electric dipole is formed that imposes a drastic effect by lowering the WF ITO 12. Polyfluorene derivatives with various kinds of polar pendant groups,12, 13, 14, 15, 16 poly(ethyleneimine),17 and ethoxylated poly(ethyleneimine)18 have been directly deposited on the surface of ITO in i‐PSCs, which show excellent capability in modifying the WF ITO and improving device performance.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Light Soaking Effects in Inverted Organic Solar Cells Functionalized with Conjugated Macroelectrolyte Electron‐Collecting Interlayers

Xia

et al. 2015

Advanced Science

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Three kinds of charged star‐shaped conjugated macroelectrolytes, named as PhNBr, TPANBr, and TrNBr, are synthesized as electron‐collecting interlayers for inverted polymer solar cells (i‐PSCs). Based on these well‐defined structured interlayer materials, the light soaking (LS) effect observed in i‐PSCs was studied systematically and accurately. The general character of the LS effect is further verified by studying additional i‐PSC devices functionalized with other common interlayers. The key‐role of UV photons was confirmed by electrochemical impedance spectroscopy and electron‐only devices. In addition, the ultraviolet photoelectron spectroscopy measurements indicate that the work function of the indium tin oxide (ITO)/interlayer cathode is significantly reduced after UV treatment. In these i‐PSC devices the LS effect originates from the adsorbed oxygen on the ITO substrates when oxygen plasma is used; however, even a small amount of oxygen from the ambient is also enough for triggering the LS effect, albeit with a weaker intensity. Our results suggest that the effect of adsorbed oxygen on ITO needs to be considered with attention while preparing i‐PSCs. This is an important finding that can aid the large‐scale manufacturing of organic solar cells via printing technologies, which do not always ensure the full protection of the device electrode substrates from oxygen.

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“…A cationic-type derivative, PFNBr, and an anionictype derivative, PFCOONa, are synthesized to produce opposite polarities. 32,33 By scanning the surface WF on PFNBr/Al and PFCOONa/Al, opposite dipoles are observed. The electric potential shift caused by the dipole at the PFNBr/Al interface is found to be ∼ 0.23 eV.…”

Section: Resultsmentioning

confidence: 99%

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

Zhong

Zhang

et al. 2017

NPG Asia Mater

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In organic electronic devices, the interfacial dipole at organic/metal interfaces is critical in determining the carrier injection or extraction that limits the performance of the device. A novel technique to enable the direct measurement of underburied dipoles is developed and demonstrated. By tilting the shadow mask by a small angle, metal atoms diffuse into the opening slit to form an ultrathin metal layer during the evaporation process. As the ultrathin metal layer cannot screen out the dipole-induced surface work function change, the dipole strength and direction at the organic/metal interface can be revealed. It was found that the polarity of the organic material, the Fermi-level pinning and the interface morphology all play important roles in dipole formation. By comparing the energy level shifts at the organic/pre-deposited metal and organic/post-deposited metal interfaces, the dipole formed by molecular interactions could be distinguished from the dipole formed by Fermi-level pinning. NPG Asia Materials (2017) 9, e379; doi:10.1038/am.2017.56; published online 19 May 2017 INTRODUCTIONIn organic electronic devices, such as organic solar cells and organic light-emitting diodes, energy-level alignment at the organic/metal interface is critical for device performance because it determines the carrier injection barrier and device built-in voltage. 1,2 A small energylevel offset between the organic material's charge transport level and the metal's Fermi level is always favored to form an ohmic contact at the interface. Therefore, metals with low work function (WF), such as Ba, Ca, Li, Cs and Al, are popular choices for cathodes to facilitate electron injection or extraction. 3-5 However, low WF metals are intrinsically unstable. As a consequence, much effort has been made to develop electrode modification materials to enable the use of stable but high WF metals as cathodes. 6 Both inorganic materials, such as alkali-metal salts and metal oxides, and organic materials, such as organic surfactants, have been successfully applied in devices. [7][8][9][10][11][12] Through the formation of a dipole layer at the organic/metal interface, induced by the interfacial interaction, the interfacial energy-level alignment is modified, leading to a reduction in the charge injection barrier. 1,13 Various molecular structures are being examined to find the best modification materials for different devices.To select the desired interfacial material, the most common characterization is measuring the WF change on substrates of the cathode metal before and after depositing the interfacial materials on top 14,15 (Figure 1a). A reduced WF indicates that the electron injection barrier is lowered and hence can be used at the cathode. In contrast, an increased WF implies that the material can be used to enhance hole injection at the anode. The deduction is straightforward for inverted devices for which the layer deposition sequence, that is, cathode

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Recent advances in water/alcohol-soluble π-conjugated materials: new materials and growing applications in solar cells

Cited by 450 publications

References 255 publications

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

High‐Performance Polymer Solar Cells Based on a Wide‐Bandgap Polymer Containing Pyrrolo[3,4‐f]benzotriazole‐5,7‐dione with a Power Conversion Efficiency of 8.63%

Understanding the Light Soaking Effects in Inverted Organic Solar Cells Functionalized with Conjugated Macroelectrolyte Electron‐Collecting Interlayers

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

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