Organic optoelectronic interfaces with anomalous transient photocurrent

Hu, Laigui; Liu, Xian; Dalgleish, Simon; Matsushita, Michio M.; Yoshikawa, Hideki; Awaga, Kunio

doi:10.1039/c5tc00414d

Cited by 50 publications

(37 citation statements)

References 111 publications

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“…Therefore, our developed composite seems to be a very promising candidate for human retinal prosthesis whose response time requirement should not be less than 70 ms. During the ON state, the transient current positively increases very quickly to fully charge the photocapacitor and then rapidly drops to a negative value with an important overshoot, showing an exponential decay that match the characteristics of double-layer capacitors under the constant-voltage mode [29]. The transient photocurrent behavior is probably due to a generation of charge carriers form a space-charge region within the semiconductor accumulated at the phosphor/polymer interface [30]. This in turn can be affected by numerous parameters like thickness of the photoactive layer, direction of illumination [31], excitation wavelength, particle content, and choice of electrode and electrolyte or solid dielectric layer.…”

Section: Resultsmentioning

confidence: 84%

High-Capacity, Fast-Response, and Photocapacitor-Based Terpolymer Phosphor Composite

et al. 2020

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This paper describes a new class of light transducer-based poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer doped with 50% wt. phosphor particles that enables to efficiently transform light energy into an electrical signal. Broadband dielectric characterization together with experimental results on photo-electric conversion demonstrated high capacitance variation of the proposed composite under light exposure, confirming promising potential of our sensor device for application in retinal prostheses where the converted electrical signal can affect the biological activity of the neuron system. In addition to the benefit of being light-weight, having ultra-flexibility, and used in a simple process, the proposed photodetector composite leads to fast response and high sensibility in terms of photoelectrical coupling where significant increases in capacitance change of 78% and 25% have been recorded under blue and green light sources, respectively. These results demonstrated high-performance material design where phosphor filler contributes to promote charge-discharge efficiency as well as reduced dielectric loss in P(VDF-TrFE-CTFE), which facilitate the composite for flexible light transducer applications, especially in the medical environment.

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Section: Resultsmentioning

confidence: 84%

High-Capacity, Fast-Response, and Photocapacitor-Based Terpolymer Phosphor Composite

et al. 2020

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“…The ratio of the value of the instantaneous current ( j t=0 ) when the light is switched on (and corresponding to the “spike”) to that of steady state current ( j ss ) after the overshoot depends on carrier recombination rate to charge transfer rate. [ 15–17 ] Obviously, j ss is more important than j t=0 for a photocatalyst. Therefore, we will use the term “photoresponse current” to refer to only j ss in the rest of this article.…”

Section: Resultsmentioning

confidence: 99%

Flexible Photocatalytic Electrode Using Graphene, Non‐noble Metal, and Organic Semiconductors for Hydrogen Evolution Reaction

et al. 2021

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Two kinds of visible light‐responsible organic semiconductors (epindolidione [EPI] and fluorinated EPI [2F‐EPI]) are synthesized. The solar hydrogen evolution photocatalytic electrode properties of the organic semiconductors are investigated and the heterostructure effect caused by manipulating the order of the deposition of 2F‐EPI and EPI is found, which increased the photoresponse current by reducing the carrier recombination of photoexcited electrons and holes. In addition, it is found that the deposition of Ni metal on the organic semiconductors further enhanced the photoresponse current and increased the durability of the organic semiconductor photocatalyst. Finally, a flexible photocatalytic electrode using graphene, organic semiconductors, and non‐noble metal cocatalyst for solar hydrogen generation is prepared. A transparent flexible electric conductive film is prepared by transfer of a graphene sheet on the polymer film. The graphene electrode is coated by two kinds of organic semiconductors layer by layer to reduce recombination of photoexcited electrons and holes. Ni metal particles are deposited on the surface of the organic semiconductor layer as a cocatalyst to improve the photocatalytic property and durability of organic semiconductors. A clear photoresponse current (about 4 μA cm−2) of the flexible photocatalytic electrode under the simulated solar light (AM 1.5 G, 100 mW cm−2) is observed.

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“…However, in all these examples, the insulator component should be sufficiently thin, or sufficiently percolated by the semiconductor, to allow the passage of a DC current upon illumination. An alternative use of insulator interlayers is to act as a blocking dielectric to accumulate free carriers formed in the semiconductor layer upon photoexcitation, and to generate a transient photocurrent response due to capacitive charging/discharging of the thick insulator dielectric 16 . The bipolar current response to light on/off is similar to that of a voltage differentiator, but where the driving voltage is the photovoltage generated across the semiconductor layer 17 .…”

Section: Introductionmentioning

confidence: 99%

Towards high-bandwidth organic photodetection based on pure active layer polarization

Reissig

Dalgleish

Awaga

2018

Sci Rep

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Organic photodetectors offer distinct advantages over their inorganic analogues, most notably through optical transparency and flexibility, yet their figures-of-merit still lag behind those of inorganic devices, and optimization strategies generally encounter a trade-off between device responsivity and bandwidth. Here we propose a novel photodetector architecture in which an organic photoactive semiconductor layer (S) is sandwiched between two thick insulating layers (I) that separate the semiconductor from the metallic contacts (M). In this architecture a differential photocurrent response is generated purely from the polarization of the active layer under illumination. Especially for an asymmetric MISIM design, where one insulating layer is a high-k ionic liquid IIL and the other a low-k polymer dielectric Ip, the responsivity/bandwidth trade-off is broken, since the role of the IIL in efficient charge separation is maintained, while the total device capacitance is reduced according to Ip. Thus the benefits of single insulating layer differential photodetectors (MISM) using either IIL or Ip are combined in a single device. Further improvements in device performance are also demonstrated by decreasing the series resistance of the photoactive layer through semiconductor:metal blending and by operation under strong background light.

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Organic optoelectronic interfaces with anomalous transient photocurrent

Abstract: In this review, anomalous transient photocurrent from organic semiconductor devices in response to square-wave light pulses in the literature are discussed; current efforts to utilize these transients are highlighted, such as in transient-type photodetectors and artificial retinas.

Cited by 50 publications

References 111 publications

High-Capacity, Fast-Response, and Photocapacitor-Based Terpolymer Phosphor Composite

High-Capacity, Fast-Response, and Photocapacitor-Based Terpolymer Phosphor Composite

Flexible Photocatalytic Electrode Using Graphene, Non‐noble Metal, and Organic Semiconductors for Hydrogen Evolution Reaction

Towards high-bandwidth organic photodetection based on pure active layer polarization

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