Subpicosecond photoinduced Stark spectroscopy in fullerene-based devices

Cabanillas‐González, Juan; Virgili, Tersilla; Alessio, Giovanni; Lüer, Larry; Lanzani, Guglielmo; Anthopoulos, Thomas D.; Leeuw, Dago M. de

doi:10.1103/physrevb.75.045207

Cited by 15 publications

(22 citation statements)

References 31 publications

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“…[ 105 ] PTSS values recovery of Δ F σ is a proof for geminate recombination and the coulombically bound nature of photogenerated pairs. [ 101 ] …”

Section: Reviewmentioning

confidence: 97%

Section: The Transient Stark Effectmentioning

confidence: 98%

Section: Picosecond E-h Distances and Charge Mobilitiesmentioning

confidence: 98%

“…[ 99 , 100 ] The transient Stark effect is manifested by a strong reduction of Δ F σ at 1 ps delay, followed fi rst by a gradual quenching evolving for several tens of picoseconds and a weak recovery, likely motivated by charge recombination ( Figure 19 ). [ 101 ] In PCBM CPG proceeds mainly by dissociation of non thermalized excitons within 100 fs. This ultrafast mechanism contrasts with the gradual evolution of Δ F σ and confi rms that the latter cannot be attributed to delayed CPG but instead to charge drift.…”

Section: The Transient Stark Effectmentioning

confidence: 99%

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Pump‐Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics

2011

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In this review we highlight the contribution of pump-probe spectroscopy to understand elementary processes taking place in organic based optoelectronic devices. The techniques described in this article span from conventional pump-probe spectroscopy to electromodulated pump-probe and the state-of-the-art confocal pump-probe microscopy. The article is structured according to three fundamental processes (optical gain, charge photogeneration and charge transport) and the contribution of these techniques on them. The combination of these tools opens up new perspectives for assessing the role of short-lived excited states on processes lying underneath organic device operation.

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“…[ 105 ] PTSS values recovery of Δ F σ is a proof for geminate recombination and the coulombically bound nature of photogenerated pairs. [ 101 ] …”

Section: Reviewmentioning

confidence: 97%

Section: The Transient Stark Effectmentioning

confidence: 98%

Section: Picosecond E-h Distances and Charge Mobilitiesmentioning

confidence: 98%

Section: The Transient Stark Effectmentioning

confidence: 99%

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Pump‐Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics

2011

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“…So far, it has been extensively used, without spatial resolution information, to characterize the internal electric field in OLEDs and solar cells based on a broad range of molecular materials, from conjugated polymers [8][9][10] to small molecules. [11][12][13][14] Combination with confocal optical microscopy allows a take-up of this technique to obtain information regarding electric field distribution across the device active area with spatial resolution higher than 1 mm. Electric field distribution is often affected by the presence of space charge in the channel, due to trapped carriers, so that upon changing the bias condition of the device it is also possible to obtain information regarding the efficiency of charge injection and charge transport.…”

Section: Introductionmentioning

confidence: 99%

Imaging the Electric‐Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy

Celebrano

Sciascia

Cerullo

et al. 2009

Adv Funct Materials

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Space resolved Stark spectroscopy is introduced as a non invasive optical technique for imaging electric field distribution in organic semiconductors. Stark spectroscopy relies on the electric field induced change in the absorption/reflection. It is shown that local monitoring of Stark shift with confocal spatial resolution provides quantitative information on the strength of the local field as well as charge distribution within the transport channel.

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Engineering Ultra Long Charge Carrier Lifetimes in Organic Electronic Devices at Room Temperature

Gao

MacKenzie

Liu

et al. 2015

Adv Materials Inter

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working devices where the band edge of the metallic contacts (typically aluminum and Indium tin oxide (ITO)) has been aligned to the highest occupied molecular orbital (HOMO)/ lowest unoccupied molecular orbital (LUMO) of the semiconductor to increase carrier injection and extraction effi ciency. However, the equilibrium Fermi level of the organic semiconductor is usually mid way between the HOMO-LUMO level, and far from that of the ITO or aluminum contact. This means for the system to reach equilibrium, and for the quasi-Fermi levels of the metal and semiconductor to align, a signifi cant number of both electrons and holes must be injected from the contacts into the bulk of the organic semiconductor, resulting in a large equilibrium background carrier population. The nongeminate recombination rate ( R ) in organic semiconductors is known to be a strong function of both local electron ( n ( x )) and local hole carrier ( p ( x )) densities, [ 20 ] ( ), , , [ 29,30 ] where k is a constant of proportionality and x is the position. Thus if the local background charge density of either species could be reduced, so would the recombination rate. Furthermore, if photogenerated electrons could be quickly swept from hole rich regions, and photogenerated holes from electron rich regions, the spatial overlap of the photogenerated populations would be reduced and charge carrier lifetime would also be increased.In the following pages we demonstrate that by engineering the band structure in a plastic electronic device, hole carrier lifetimes longer than 1 hour can be achieved. We attribute this four order of magnitude increase in carrier lifetime to a hill shaped band structure which forces photogenerated electrons and holes to spatially separate shortly after generation, the reduction in spatial overlap between the electron and hole population reduces the recombination rate. The hill shaped band structure also generates a hole rich and electron poor region in the center of the device in which the hole recombination rate is low, this acts as a charge storage area. These results demonstrate that it is possible for organic semiconductors to have long charge carrier lifetimes, and opens up the possibility for new classes of ultra low light level photodetectors and memory elements.Figure 1 a depicts the device structure; it consists of an ITO coated glass substrate with contact resistance 30 Ω sq −1 . An insulating layer of SiO 2 is spin coated from a sol-gel onto the ITO fi lm, followed by a layer of the organic semiconductor N,N′-Di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl)-4,4′-diamine (NPB). Finally a 30 nm thick aluminum capping electrode is evaporated onto the NPB. Full details of device fabrication can be found in the Supporting Information. Charge is stored within the device by photoexcitation through the transparent ITO contact using a 355 nm laser with a 10 ns pulse Plastic electronic devices fabricated from carbon based molecules and polymers [ 1 ] have received considerable academic and industrial attention over the l...

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Subpicosecond photoinduced Stark spectroscopy in fullerene-based devices

Cited by 15 publications

References 31 publications

Pump‐Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics

Pump‐Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics

Imaging the Electric‐Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy

Engineering Ultra Long Charge Carrier Lifetimes in Organic Electronic Devices at Room Temperature

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