Design Considerations for Electrode Buffer Layer Materials in Polymer Solar Cells

Bilby, David; Frieberg, Bradley; Kramadhati, Shobhita; Green, Peter; J, Kim

doi:10.1021/am502673e

Cited by 43 publications

(22 citation statements)

References 49 publications

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“…However, the formation of interface dipole at the ITO surface by self‐assembly of PVPy can be possible through the weak interaction between pyridyl ring and free hydroxyl group on the surface of ITO. Because of its weaker basicity than those of PEI or PAA, a magnitude of dipole moment by the formation of interface dipole would be smaller than those of PEI or PAA, indicating the performance of the device with PVPy was poorer than the device with PEI or PAA in addition to the device with ethoxylated PEIE …”

Section: Resultssupporting

confidence: 88%

“…Because of its weaker basicity than those of PEI or PAA, a magnitude of dipole moment by the formation of interface dipole would be smaller than those of PEI or PAA, indicating the performance of the device with PVPy was poorer than the device with PEI or PAA in addition to the device with ethoxylated PEIE. 32,33 We fabricated cPSCs with a structure of ITO/PEDOT/ active layer/PVPy/Al to investigate the effect of thin layer of PVPy as an IFL at the interface between the active layer and the Al cathode on the photovoltaic properties. Polar components such as pyridine in the polymer backbone will be accumulated at the top of the PVPy surface due to the repulsive interaction between the polar component and the hydrophobic active layer, indicating that the spontaneous organization of PVPy occurs during the spin coating process.…”

Section: Articlementioning

confidence: 99%

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Self‐assembled Poly(4‐vinylpyridine) As an Interfacial Layer for Polymer Solar Cells

Sylvianti

Trang

Marsya

et al. 2015

Bulletin Korean Chem Soc

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A nonconjugated polymer, poly(4‐vinylpyridine) (PVPy), is applied to polymer solar cells (PSCs) as an interfacial layer (IFL) either inverted or conventional type PSCs. The Kelvin probe microscopy measurements support the formation of favorable interface dipole at the cathode interface, indicating the reduction of an electron collection barrier from the active layer to the cathode. Inverted type PSC with PVPy as an IFL demonstrate the power conversion efficiency (PCE) of 3.20%, (open circuit voltage [V oc] = 0.61 V, short circuit current [J sc] = 8.68 mA/cm2, fill factor [FF] = 59.4%), which is better than the device without interlayer (PCE = 2.95%, V oc = 0.60 V, J sc = 8.11 mA/cm2, FF = 60.6%). Most increase in the PCE of the devices with interlayer is resulted from enhancement of the J sc. This is due to that the reduction of an electron collection barrier at the cathode interface. Conventional type PSC with PVPy (3.51%) at the cathode interface also exhibits better the PCE compared to that of the device without interlayer (2.88%).

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Section: Resultssupporting

confidence: 88%

Section: Articlementioning

confidence: 99%

Self‐assembled Poly(4‐vinylpyridine) As an Interfacial Layer for Polymer Solar Cells

Sylvianti

Trang

Marsya

et al. 2015

Bulletin Korean Chem Soc

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“…Polymer solutions were typically cast at 3000 rpm for 30 s from 2 mg per mL solvent: poly(vinyl alcohol) 100% hydrolyzed (PVA), poly(sodium styrene sulfonate) (PSS:Na), poly(styrenesulfonic acid) (PSS Acid), poly (acrylic acid) (PAA), poly(acrylamide) (PAAm), poly (acrylic acid) sodium salt (PAA:Na), and PDDA:Cl were cast from water; poly(ethylenimine) (PEI), PEIE (both at 0.4 wt%), and poly(vinylphenol) (PVPhOH) are cast from 2‐methoxyethanol; polystyrene (PS) was cast from toluene. For comparison, the clean ITO sample was prepared and measured, and all of polymer samples were spin cast onto ITO and measured in air using a homemade Kelvin probe microscope . C‐AFM and KPFM measurements were performed using Asylum Research MFP‐3D under ambient conditions.…”

Section: Methodsmentioning

confidence: 99%

Work Function Modification via Combined Charge‐Based Through‐Space Interaction and Surface Interaction

Yang

Bilby

Chung

et al. 2018

Adv Materials Inter

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organic solar cells (OSCs) for several reasons: it is transparent in the visible region and it has not only high conductivity but also the capability to collect either electrons or holes through work function modification. [20] To illustrate, inverted OSCs, which have been extensively studied due to their superior long term ambient stability and printability relative to conventional OSCs, use ITO as a cathode by controlling its work function. [15,21,22] Thus, understanding the origin of the work function modification process is of critical importance for organic electronic devices. Currently, introducing a thin layer of interfacial materials between the electrode and the active layer is studied to modify the work function of the electrode through the formation of interfacial dipole interactions. For example, He et al. reported that the efficiency of OSCs can be raised to 9.2% by effective work function tuning with an alcohol/water-soluble conjugated polymer. [6] Lee et al. showed that high performance OSCs with 8.32% efficiency could be fabricated using a combination of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) and nonconjugated polyelectrolytes as recombination layers that lead to effective work function reduction at the ITO electrode. [15] Additionally, both anionic and cationic polyelectrolyte interlayers have been studied to achieve a proper energy level alignment for Work function modification of electrodes is an important factor to achieve high performance in organic electronics. However, a clear explanation of the origin of work function modification has remained elusive. Here, it is investigated how the work function of electrodes is affected by the chargebased through-space interaction with the well-known surface interaction. The studies reveal that the formation of a surface dipole leads to a work function shift, even when the work function modifying layer and substrate are separated. A work function shift is also demonstrated by electrophoretic deposition of ionic polyelectrolytes while the same polyelectrolytes do not cause any work function shift when they are spin cast. More noteworthy is that a neutral (nonionic) polymer which has no specific surface-interacting functional groups can induce work function shift of its substrate by a chargebased through-space interaction when deposited by electrospraying. These results provide a more comprehensive understanding of work function modification and motivate the design and selection of a wide range of effective work function modifying layers for organic electronics.

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“…Thus, it is highly desired to develop alternative CIL materials which can be facilely prepared at relatively low temperature. Recently, several other low‐temperature solution‐processed CIL materials have been reported, including water/alcohol soluble conjugated/non‐conjugated polymers, small organic molecules, and fullerene derivatives, which are mostly organic materials, and their long‐term stabilities need to be concerned. Hence, exploiting novel inorganic CIL materials is of high importance for commercial applications of iPSCs.…”

Section: Introductionmentioning

confidence: 99%

Beyond Metal Oxides: Introducing Low‐Temperature Solution‐Processed Ultrathin Layered Double Hydroxide Nanosheets into Polymer Solar Cells Toward Improved Electron Transport

Liu

Chen

et al. 2018

Solar RRL

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Metal oxides such as zinc oxide (ZnO) have been commonly used as the cathode interfacial layer (CIL) of bulk heterojunction inverted polymer solar cells (BHJ‐iPSCs), for which a high‐temperature annealing treatment is usually required to improve their CIL performance. Layered double hydroxides (LDHs) are a class of inorganic two‐dimensional (2D) nanomaterials composed of positively charged brucite‐like layers intercalated with charge‐balancing anions and water molecules, showing potential applications in catalysis, adsorption, electrochemical energy storage and conversion, etc., but have never been applied in PSCs. Herein, for the first time LDH nanosheets are applied in BHJ‐iPSC devices as a novel CIL substituting the commonly used ZnO, affording an obvious efficiency enhancement relative to ZnO‐based device. Ultrathin MgxAl‐NO3‐LDH nanosheets are prepared by ultrasonication‐assisted liquid exfoliation of bulk MgxAl‐NO3‐LDHs prepared via a co‐precipitation method, and deposited onto an ITO substrate as a CIL by a low‐temperature solution‐processed technique. Based on MgxAl‐NO3‐LDH CIL, BHJ‐iPSC devices with the poly(4,8‐bis‐alkyloxybenzo(l,2‐b:4,5‐b′)‐dithiophene‐2,6‐diylalt‐(alkylthieno(3,4‐b) thiophene‐2‐carboxylate)‐2,6‐diyl):[6,6]‐phenyl C71‐butyric acid methyl ester (PBDTTT‐C:PC71BM) photoactive layer exhibits an improvement of power conversion efficiency relative to those based on ZnO CIL. This is primarily originated from the increase of fill factor due to the improved interfacial contact between the ITO and active layer, facilitating the interfacial electron transport.

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Design Considerations for Electrode Buffer Layer Materials in Polymer Solar Cells

Cited by 43 publications

References 49 publications

Self‐assembled Poly(4‐vinylpyridine) As an Interfacial Layer for Polymer Solar Cells

Self‐assembled Poly(4‐vinylpyridine) As an Interfacial Layer for Polymer Solar Cells

Work Function Modification via Combined Charge‐Based Through‐Space Interaction and Surface Interaction

Beyond Metal Oxides: Introducing Low‐Temperature Solution‐Processed Ultrathin Layered Double Hydroxide Nanosheets into Polymer Solar Cells Toward Improved Electron Transport

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