Effects of Impurities on Operational Mechanism of Organic Bulk Heterojunction Solar Cells

Kaake, Loren G.; Dang, Xuan‐Dung; Leong, Wei Lin; Zhang, Yuan; Heeger, Alan J.; Nguyen, Thuc‐Quyen

doi:10.1002/adma.201203786

Cited by 43 publications

(30 citation statements)

References 30 publications

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“…Measurements revealed increased polaron trapping and trap-induced recombination. This conclusion was confirmed in a more recent study 75 where the photophysical processes associated with impurities were analyzed and compared with the results obtained upon doping with PC 84 BM and 7,7,8,.…”

Section: Iii1a Basics Of Solar Cellssupporting

confidence: 71%

Fullerene derivatives as nano-additives in polymer composites

Penkova¹,

Acquah²,

Piotrovskiy³

et al. 2017

Russ. Chem. Rev.

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Section: Iii1a Basics Of Solar Cellssupporting

confidence: 71%

Fullerene derivatives as nano-additives in polymer composites

Penkova¹,

Acquah²,

Piotrovskiy³

et al. 2017

Russ. Chem. Rev.

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“…[10–14] Quite a bit of work is dedicated to identifying and minimizing the effect of impurities on the electrical properties of organic semiconductors. [15–17] With the exception of a few reports, however, the impact of the isomer structure and/or co-existence has been mostly unexplored. In anthradithiophene (ADT), for example, organic field-effect transistor (OFET) devices fabricated on the anti -isomer surpassed those based on syn -isomer by more than one order of magnitude in measured mobility.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Isomer Purity on Trap States and Performance of Organic Thin‐Film Transistors

Diemer

Hayes

Welchman

et al. 2016

Adv Elect Materials

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Organic field-effect transistor (OFET) performance is dictated by its composition and geometry, as well as the quality of the organic semiconductor (OSC) film, which strongly depends on purity and microstructure. When present, impurities and defects give rise to trap states in the bandgap of the OSC, lowering device performance. Here, 2,8-difluoro-5,11-bis(triethylsilylethynyl)-anthradithiophene is used as a model system to study the mechanism responsible for performance degradation in OFETs due to isomer coexistence. The density of trapping states is evaluated through temperature dependent current-voltage measurements, and it is discovered that OFETs containing a mixture of syn- and anti-isomers exhibit a discrete trapping state detected as a peak located at ~ 0.4 eV above the valence-band edge, which is absent in the samples fabricated on single-isomer films. Ultraviolet photoelectron spectroscopy measurements and density functional theory calculations do not point to a significant difference in electronic band structure between individual isomers. Instead, it is proposed that the dipole moment of the syn-isomer present in the host crystal of the anti-isomer locally polarizes the neighboring molecules, inducing energetic disorder. The isomers can be separated by applying gentle mechanical vibrations during film crystallization, as confirmed by the suppression of the peak and improvement in device performance.

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“…A defect concentration of 0.01-0.1% is known to reduce solar cell performance by 20-50%, 64,65 and with a photobleach rate of 4% per hour, the illumination time needed to photochemically introduce such a number of defects (corresponding 0.01-0.1% bleach of PCDTBT) in an environment with 0.1 ppm O 2 is 5100 -51000 h (SI for details). This simple "back-of-the envelope" calculation matches the observed lifetime (41000 h) of PCDTBT solar cells in such an environment.…”

Section: Bond Twisting and Photobleach Ratementioning

confidence: 99%

Molecular Packing and Arrangement Govern the Photo-Oxidative Stability of Organic Photovoltaic Materials

et al. 2015

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For long-term performance chemically robust materials are desired for organic solar cells (OSCs). Illuminating neat films of OSC materials in air and tracking the rate of absorption loss, or photobleaching, can quickly screen a material's photo-chemical stability. In this report, we photobleach neat films of OSC materials including polymers, solution-processed oligomers, solution-processed small molecules, and vacuum-deposited small molecules. Across the materials we test, we observe photobleaching rates that span seven orders of magnitude. Furthermore, we find that the film morphology of any particular material impacts the observed photobleaching rate, and that amorphous films photobleach faster than crystalline ones. In an extreme case, films of amorphous rubrene photobleach at a rate 2500 times faster than polycrystalline films. When we compare density to photobleaching rate, we find that stability increases with density. We also investigate the relationship between backbone planarity and chemical reactivity. The polymer PBDTTPD is more photostable than its more twisted and less ordered furan derivitative, PBDFTPD. Finally, we relate our work to what is known about the chemical stability of structural polymers, organic pigments, and organic light emitting diode materials. For the highest chemical stability, planar materials that form dense, crystalline film morphologies should be designed for OSCs.

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Effects of Impurities on Operational Mechanism of Organic Bulk Heterojunction Solar Cells

Cited by 43 publications

References 30 publications

Fullerene derivatives as nano-additives in polymer composites

Fullerene derivatives as nano-additives in polymer composites

The Influence of Isomer Purity on Trap States and Performance of Organic Thin‐Film Transistors

Molecular Packing and Arrangement Govern the Photo-Oxidative Stability of Organic Photovoltaic Materials

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