Photocurrent multiplication in organic single crystals

Hiramoto, Masahiro; Miki, Ayako; Yoshida, Minoru; Yokoyama, Masaaki

doi:10.1063/1.1501764

Cited by 40 publications

(36 citation statements)

References 4 publications

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“…[18,19] Since the dark current is not controlled by carrier tunneling across a high contact barrier, this casts doubts in the applicability to our devices of the model of photoinduced tunneling injection proposed elsewhere. [5][6][7][8] Figure 1f shows the current density J dc and the multiplication factor g mult as functions of the applied direct-current (DC) voltage measured on a single F 16 CuPc layer contacted by poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and Au for several incident light intensities of wavelength 633 nm. The maximum value of g mult exceeds 3000 %; the quantum efficiency is nearly symmetric with respect to the voltage bias and increases upon increasing voltage, as predicted by Equation 1.…”

Section: Single-layer Devices Of F 16 Cupcmentioning

confidence: 99%

“…[4] However, other mechanisms could be responsible for photomultiplication in devices based on these materials. Hiramoto and co-workers found photomultiplication in organic diodes [5][6][7][8][9] that resulted from improved electron tunneling across the metal-organic contact upon carrier photogeneration and trapping in the bulk. Friend and co-workers observed apparent photomultiplication in an ambipolar polymer.…”

Section: Introductionmentioning

confidence: 99%

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Photomultiplication in Disordered Unipolar Organic Materials

et al. 2006

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Photomultiplication in conventional inorganic semiconductors has been known and used for decades, the underlying mechanism being multiplication by impact ionization triggered by hot carriers. Since neither carrier heating by an electric field nor avalanche multiplication are possible in strongly disordered organic solids, charge multiplication seems to be highly unlikely in these materials. However, here the photomultiplication observed in the bulk of a unipolar disordered organic semiconductor is reported. The proportion of extracted carriers to incident photons is experimentally determined to be in excess of 3000 % in a single‐layer device of the air‐stable, n‐type organic semiconductor F16CuPc (Pc: phthalocyanine). This effect is explained in terms of exciton quenching by localized charges, the subsequent promotion of these detrapped charges to the high‐mobility energy band of the density‐of‐states (DOS) distribution, and subsequent slow equilibration within this broad intrinsic DOS. Such a mechanism allows multiple replenishment of the optically released charge by mobile carriers injected from an Ohmic electrode. Also shown is photomultiplication in double‐layer devices composed of layers of donor and acceptor small‐molecule materials. This result implies that, apart from exciton dissociation at a donor/acceptor interface, exciton energy transfer to trapped carriers is a complementary photoconductivity process in organic solar cells. This new insight paves the way to cheap, highly efficient organic photodetectors on flexible substrates for numerous applications.

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Section: Single-layer Devices Of F 16 Cupcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photomultiplication in Disordered Unipolar Organic Materials

et al. 2006

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“…[36] Inspired by this work, a series of PM type OPDs are realized during the past decades. [37][38][39][40][41][42][43][44][45][46][47] There are many efforts concentrated on the research of the working mechanisms of PM, [48][49][50][51][52] the improvement of device performance, [53][54][55][56][57][58][59] and the adjustment of spectral response window. [60][61][62][63][64] However, to date, a comprehensive review about PM type OPDs has not yet been published.…”

Section: Introductionmentioning

confidence: 99%

Recent Progress on Photomultiplication Type Organic Photodetectors

Miao

Zhang

2018

Laser & Photonics Reviews

222

182

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Photodetectors as a significant unit of intelligent optoelectronic systems have stimulated immense attention from multidisciplinary areas. Photomultiplication (PM) is desirable for sensitive photodetectors with strong detection capability of weak light, which can further simplify the photo‐detection systems without pre‐amplifier circuit. For organic photodetectors (OPDs), PM phenomenon cannot be realized by utilizing the principle of avalanche effect or impact ionization as in inorganic materials, stemming from organic semiconductor materials with large exciton binding energy and disordered structure. In this review, the recent progress on PM type OPDs is comprehensively summarized from the perspective of device physics and material science. Charge tunneling injection induced by interfacial traps becomes the mainstream working mechanism for obtaining PM phenomenon. A series of PM type OPDs was achieved by utilizing interfacial blocking layer and introducing trap states into active layer or interfacial layer. The filter‐free PM type narrowband OPDs are realized by combining the concept of charge injection narrowing with the mechanism of PM. Meanwhile, further development on this hot topic is proposed and fully discussed, including multifunctional OPDs, organic–inorganic hybrid photodetectors, and photodetector systems.

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“…Observing the relation between J ph and G in (2a), there is a three-quarters power dependence, which implies that gains contributed by the bulk material will be <1 unless there are photodependent charge injection mechanisms. Photodependent contact injection dominates in thin devices, sometimes leading to very large gains [5]. In thicker devices, gains >1 are achievable especially at low light levels.…”

Section: Space Charge Limited Photocurrent Model and Bulk Photoconmentioning

confidence: 99%

Photoconductivity and Photoconductive Gain in Organic Bulk Heterojunction Materials

Liang

Danielson

Ooi

et al. 2015

IEEE Trans. Electron Devices

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A comprehensive study on photoconductive gain in organic bulk heterojunction (OBHJ) materials is reported. High photoconductive gains in OBHJs occur in operating regions where the device characteristics are dominated by photomodulated contact injection effects. The photomodulated injection current contributes to the total device current by augmenting the photocurrent resulting from photoabsorption in the device. An experimentally confirmed simulation of bulk photoconduction in lateral P3HT:PC 71 BM bulk heterojunction blend devices is presented, and it clarifies the origins and operating regimes in these devices. High gains occur at lower light intensities, where the total device current is dominated by photomodulated contact injection rather than bulk photoconduction effects. At higher light intensities, the total device current is dominated by bulk photoconduction effects, where the photocurrent results from light absorption in the bulk material. In agreement with previous research, gains also increase with higher applied biases. The inclusion of field-dependent mobilities plays a critical role in accurately modeling this relationship between applied voltage bias and gain.

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Photocurrent multiplication in organic single crystals

Abstract: High charge carrier densities and conductance maxima in single-crystal organic field-effect transistors with a polymer electrolyte gate dielectric

Cited by 40 publications

References 4 publications

Photomultiplication in Disordered Unipolar Organic Materials

Photomultiplication in Disordered Unipolar Organic Materials

Recent Progress on Photomultiplication Type Organic Photodetectors

Photoconductivity and Photoconductive Gain in Organic Bulk Heterojunction Materials

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