Efficient inverted polymer solar cells employing favourable molecular orientation

Vohra, Varun; Kawashima, Konosuke; Kakara, Takeshi; Koganezawa, Tomoyuki; Osaka, Itaru; Takimiya, Kazuo; Murata, Hideyuki

doi:10.1038/nphoton.2015.84

Cited by 796 publications

(648 citation statements)

References 40 publications

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“…1,2 Research in the field of solution processed organic photovoltaics (OPV) has mostly focused on blends of conjugated polymers with fullerenes due to their high efficiency that has reached 11% in multijunctions 3 and above 10% in single junctions. [4][5][6] Recently organic solar cells based on low molecular weight solution processed semiconductor molecules (so called "small molecule" organic solar cells)…”

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confidence: 99%

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

et al. 2016

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We analyze the voltage losses at open circuit in solutionprocessed, small-molecule:fullerene blend solar cells, using electroluminescence and external quantum efficiency measurements and the reciprocity relationship between light absorption and emission. For solar cells made from oligothienylenevinylene-based donors and phenyl-C 71 butyric acid methyl ester (PC 71 BM), we find that the voltage loss due to the finite breadth of the absorption edge is remarkably small, less than 0.01 eV in the best cases, while the voltage loss due to nonradiative recombination reaches 0.29 eV, one of the smallest values reported for an organic solar cell. As a result, the open-circuit voltage reaches around 1.0 V for an optical gap of 1.6 eV, greatly exceeding the voltage of a high-performance polymer-based system with similar optical gap. We assign the remarkably small absorption broadening loss to a low degree of energetic disorder in the small-molecule system that allows efficient charge separation at a lower driving force than in typical conjugated polymer blends.

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confidence: 99%

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

et al. 2016

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“…The devices showed a typical p-type transporting characteristic measured under ambient conditions. The PSTDPP based OFET exhibited relatively high hole mobility of 2.2 × 10 −3 cm 2 ·V −1 ·s −1 with an on/off ratio of 10 6 . The high mobility of the PSTDPP could be ascribed to the better molecular organization in the film.…”

Section: Hole Mobilitymentioning

confidence: 99%

“…Since different active layer films prepared by diverse solvents have, respectively, special surface energy, reflecting the surface composition of blend film. Furthermore, the performance of BHJ solar cell in part depends on whether polymer or [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) would be enriched on the top surface of the blend film [19]. Besides, mixed solvents can also be effectively used to tune the miscibility of the donor and acceptor components, the domain size and the morphology of active layer, which play an important role in optimizing the photovoltaic performances for PSCs [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Improving the Performances of Random Copolymer Based Organic Solar Cells by Adjusting the Film Features of Active Layers Using Mixed Solvents

et al. 2015

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A novel random copolymer based on donor-acceptor type polymers containing benzodithiophene and dithienosilole as donors and benzothiazole and diketopyrrolopyrrole as acceptors was designed and synthesized by Stille copolymerization, and their optical, electrochemical, charge transport, and photovoltaic properties were investigated. This copolymer with high molecular weight exhibited broad and strong absorption covering the spectra range from 500 to 800 nm with absorption maxima at around 750 nm, which would be very conducive to obtaining large short-circuits current densities. Unlike the general approach using single solvent to prepare the active layer film, mixed solvents were introduced to change the film feature and improve the morphology of the active layer, which lead to a significant improvement of the power conversion efficiency. These results indicate that constructing random copolymer with multiple donor and acceptor monomers and choosing proper mixed solvents to change the characteristics of the film is a very promising way for manufacturing organic solar cells with large current density and high power conversion efficiency.

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“…Currently, photoconversion efficiencies (PCEs) over 10% have been demonstrated for a single bulk heterojunction structure with a suitable polymer side chain. [1][2][3] In addition, engineering a band structure is an important issue, and the the OPV energy diagram shows that the process of engineering the band structure affect both the initial photovoltaic performance and long-term stability of OPV cells. This is because the large energy gap between two adjacent layers causes an unexpected thermal loss without any power generation and the defects generally act as carrier traps.…”

Section: Introductionmentioning

confidence: 99%

Inverted Organic Photovoltaic Cell with ZnO Nanorod Structure

Fukuda

Uratani

2017

Electrochemistry

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The electrical and physical properties at the interface between the ZnO electron transport/collection layer and an organic photoactive layer play important roles in determining photovoltaic performance. Therefore, we have fabricated ZnO nanorods and optimized the coating conditions used for deposition of the ZnO seed layer, which serves as a nucleation site for crystal growth. First, the relationship between the concentration of the ZnO precursor solution (zinc acetate dihydrate and hexamethylenetetramine in methanol) and diameter of the ZnO nanorods was examined, and we showed that the diameter continuously decreased with increasing concentration, reaching a minimum of 23 nm. Further, we investigated density of ZnO nanorods and photovoltaic performance of the inverted cell as a function of the rotation speed used during the spin coating process to deposit the ZnO seed layer. A low density of ZnO nanorods was obtained when the rotation speed was low, and this caused the short circuit current density, open circuit voltage, and fill factor of the organic photovoltaics to decrease. As a result, a maximum photoconversion efficiency of 3.0% was achieved, and this value was 1.6-fold greater than that measured using a reference device containing no ZnO nanorods (photoconversion efficiency: 1.9%).

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Efficient inverted polymer solar cells employing favourable molecular orientation

Cited by 796 publications

References 40 publications

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

Low Open-Circuit Voltage Loss in Solution-Processed Small-Molecule Organic Solar Cells

Improving the Performances of Random Copolymer Based Organic Solar Cells by Adjusting the Film Features of Active Layers Using Mixed Solvents

Inverted Organic Photovoltaic Cell with ZnO Nanorod Structure

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