Investigation of Charge Accumulation States in Polymer Solar Cells using Light-Induced Electron Spin Resonance Spectroscopy

Yabusaki, Masaki; Marumoto, Kazuhiro

doi:10.2494/photopolymer.31.169

Cited by 9 publications

(30 citation statements)

References 27 publications

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“…Particularly, the EDMR line shape was unchanged between the cases of the film orientation perpendicular and parallel to the static field. This result suggests that the signal arises from spin species in the random chain orientation, consistent with the previous references that suggested the signals originating from hole carriers on P3HT chains with random orientation. − The narrow component is, thus, contributed by the hole carrier, meaning that the broad component could be contributed by electron carriers. Concerning the line width, in a recent report on polymer LEDs, the spectral component from a hole of the EDMR signal was suggested to give a narrower spectrum in the double-Gaussian model.…”

Section: Resultssupporting

confidence: 89%

“…We here discuss the ESR parameters obtained from the double-Gaussian model. First, the g -value of the narrow component (2.0020) coincides with the g -values of hole carriers of P3HT determined by ESR for solar cells − and is close to the g -center value (2.0018) of an iodine-doped spin-coated P3HT film determined by W-band ESR spectroscopy . Particularly, the EDMR line shape was unchanged between the cases of the film orientation perpendicular and parallel to the static field.…”

Section: Resultssupporting

confidence: 79%

“…Such a SOC-broadening effect was recently suggested for poly( p -phenylene vinylene) (PPV) derivatives, , and this effect is expected to be more pronounced in P3HT by the sulfur atom. We note that an ESR component with a g -factor and line width similar to those of the broad component in the present study was observed from a solar cell containing P3HT under photoexcitation, and the signal was attributed to accumulated holes at polymer-chain ends with bromine atoms. − This assignment would not be appropriate for the present EDMR spectrum because the absence of an EDMR signal in the hole-only diode can deny the coexistence of two types of hole signals. On the basis of these discussions, we conclude that the broad and narrow components in the EDMR spectrum of a P3HT diode originate from electron and hole carriers, respectively, forming e–h pairs.…”

Section: Resultsmentioning

confidence: 55%

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Electron–Hole Pairs Generated in the Crystalline Phase of Polymer Diodes Studied by Electrically Detected Magnetic Resonance Techniques

Iwamoto¹,

Hayakawa²,

Hatanaka³

et al. 2019

J. Phys. Chem. C

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The properties of electron−hole (e−h) pairs generated in a working poly(3-hexylthiophene) (P3HT) diode are investigated by electrically detected magnetic resonance (EDMR) techniques. The EDMR intensity is shown to increase with increasing density of injected electrons for a given hole density, demonstrating that the EDMR signal arises from an e−h pair. The EDMR spectrum consists of two Gaussian curves, one of which gives a g-value very similar to that of hole carriers, suggesting that the EDMR spectrum is given by the sum of electron spin resonance (ESR) spectra from hole and electron carriers forming e−h pairs. Bias-dependent correlation between carriers and e−h pairs under diode operation is examined directly from independent measurements of near-infrared (NIR) spectroscopy for carriers and EDMR for e−h pairs. When the bias is increased to above a threshold, the EDMR signal is strongly reduced despite a gradual increase in the NIR signals, providing evidence that the e−h pairs are dissociated by an electric field in the bias region. Because of this property of the pair, the correlation between the carriers and e−h pairs inside the diode changes depending on the bias magnitude: the carriers and e−h pairs coexist or only the carriers exist. The e−h pair is presumed to be formed across different lamellae because of the crystalline phase of the P3HT film. Although the intensity of the EDMR signal from the interlamellar e−h pair is small, the intensity increases substantially when the sample is exposed to air, suggesting the formation of a magnetoreactive species that incorporates oxygen.

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Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 55%

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Electron–Hole Pairs Generated in the Crystalline Phase of Polymer Diodes Studied by Electrically Detected Magnetic Resonance Techniques

Iwamoto¹,

Hayakawa²,

Hatanaka³

et al. 2019

J. Phys. Chem. C

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“…The estimated B 1/2 values for C n and C b are 0.17 and 0.60 mT, respectively, which are broader than those estimated from the 179 MHz EDMR spectrum. Because the estimated g -factor for the C n component is close to that of holes in P3HT, − the C n and C b components are attributed to the ESR of holes and electrons, respectively …”

Section: Resultsmentioning

confidence: 90%

Recombination of Free Carriers and Space Charges in Poly(3-hexylthiophene), as Revealed by Electrically and Capacitively Detected Magnetic Resonances

Wakikawa

Ikoma

2020

J. Phys. Chem. C

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Using electrically and capacitively detected magnetic resonance (EDMR and CDMR) techniques, we clarified recombination in regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) films, which is an important elementary process for photoconduction. The modulation frequency dependences of the EDMR and CDMR reveal the coexistence of two types of electron− hole (e−h) pairs with different lifetimes in the device fabricated with a Schottky contact between P3HT and an Al electrode. The short-lived e−h pair is a precursor of the recombination of free carriers in the bulk P3HT. The long-lived e−h pair is involved in the recombination of space charges in the Schottky junction region, which leads to an enhancement of the photocurrent.

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“…In this mode, carriers can be stored in the interface between insulator and semiconductor until the linearly increasing voltage is applied. Additionally, it is reported that light-induced electron spin resonance (ESR) spectroscopy can contribute to the analysis of charge accumulation states [ 41 ].…”

Section: Introductionmentioning

confidence: 99%

A New Benchmark of Charges Storage in Single-Layer Organic Light-Emitting Diodes Based on Electrical and Optical Characteristics

Zhang

Wang

et al. 2021

Molecules

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The storage of charges in organic light-emitting diodes (OLEDs) has drawn much attention for its damage to device performance as well as the loss to carriers. Thus, it is essential to address the issue and do further investigation. The traditional approach to storage analysis is mainly based on transient measurement since it is sensitive to transient instead of steady signal. In this paper, we proposed a new benchmark to investigate the single-layer OLEDs capable of stored charges with poly (methyl methacrylate) (PMMA), which is just based on electrical and optical characteristics. Since the stored charges contribute both to luminance and current of the devices with PMMA, the area between them can be taken as a benchmark and evaluated the storage of charges. In our experiment, the areas of 4 nm, 6 nm, 8 nm, and 10 nm PMMA devices are 0.348, 0.554, 0.808, and 0.894, respectively, indicating a higher capability of storage in thicker PMMA. It is exactly in line with the results taken from transient electroluminescence (EL) measurement. Thus, this new benchmark is practical and provides a more accessible approach to investigate the storage of charges in OLEDs.

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Investigation of Charge Accumulation States in Polymer Solar Cells using Light-Induced Electron Spin Resonance Spectroscopy

Cited by 9 publications

References 27 publications

Electron–Hole Pairs Generated in the Crystalline Phase of Polymer Diodes Studied by Electrically Detected Magnetic Resonance Techniques

Electron–Hole Pairs Generated in the Crystalline Phase of Polymer Diodes Studied by Electrically Detected Magnetic Resonance Techniques

Recombination of Free Carriers and Space Charges in Poly(3-hexylthiophene), as Revealed by Electrically and Capacitively Detected Magnetic Resonances

A New Benchmark of Charges Storage in Single-Layer Organic Light-Emitting Diodes Based on Electrical and Optical Characteristics

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