Three-layer Stacked Color Image Sensor With 2.0-μm Pixel Size Using Organic Photoconductive Film

Togashi, Hiroyuki; Yagi, Iwao; Murata, Maasa; Kuribayashi, Masaru; Koga, F.; Yamaguchi, Tsutomu; Oike, Yusuke; Ezaki, Takayuki; Hirayama, Teruo; Watanabe, T.; Joei, Masahiro; Hayashi, T.; Hirata, Shuzo; Fukuoka, Shima; Ando, Yoichi; Sato, Yoshiaki; Yamamoto, J.

doi:10.1109/iedm19573.2019.8993553

Cited by 9 publications

(7 citation statements)

References 3 publications

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“…In addition, indium–tin–zinc–oxide (ITZO) was used as a high-mobility active channel material for the TFTs − to accommodate a smaller pixel size of 20 μm and a higher number of pixels of 320 × 240 (QVGA). The color video imaging operation of the sensor was confirmed, and spectral crosstalk lower than those of the previous three-layer-stacked sensors mentioned in refs and was achieved, especially in the R-light region, through the integration of the CIS and two color-selective OPFs.…”

Section: Introductionsupporting

confidence: 56%

“…Comparing this work with ref , the responses of the G and B channels at 650 nm were markedly reduced from 0.87 and 0.25 to 0.08 and <0.02, respectively. In addition, the response of the B channel was also markedly reduced from 0.44 mentioned in ref to <0.02. At 550 nm, the responses of the R and B channels in this work (0.016 and <0.02, respectively) were lower than those mentioned in ref (both 0.44).…”

Section: Results and Discussionmentioning

confidence: 78%

“…Moreover, a three-layer-stacked color image sensor comprising two-layerstacked Si PDs on a Si substrate and an OPF for detecting green light above the Si PDs to improve the spectral characteristics was reported. 13 However, spectral crosstalk was still observed between the Si PDs for B and R light.…”

Section: Introductionmentioning

confidence: 99%

“…In this type of sensor, three primary colors are separated in the depth direction by utilizing the difference between the penetration depths of R, G, and B light in Si; however, there is a significant amount of color crosstalk between the R, G, and B channels because Si intrinsically absorbs light in the entire visible region. Moreover, a three-layer-stacked color image sensor comprising two-layer-stacked Si PDs on a Si substrate and an OPF for detecting green light above the Si PDs to improve the spectral characteristics was reported . However, spectral crosstalk was still observed between the Si PDs for B and R light.…”

Section: Introductionmentioning

confidence: 99%

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Color-Filter-Free Three-Layer-Stacked Image Sensor Using Blue/Green-Selective Organic Photoconductive Films with Thin-Film Transistor Circuits on CMOS Image Sensors

Sakai¹,

Takagi²,

Imamura³

et al. 2021

ACS Appl. Electron. Mater.

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In this paper, we describe a three-layer-stacked color image sensor comprising two organic photoconductive films (OPFs) with thin-film transistor-based readout circuits and a complementary metal–oxide–semiconductor (CMOS) image sensor. In this three-layer-stacked sensor, a blue-sensitive OPF selectively absorbs blue light, a green-sensitive OPF selectively absorbs green light, and a CMOS image sensor (CIS) receives red light. Color video imaging operation at 60 frames per second was confirmed for a prototype sensor having 320 × 240 pixels with a pixel pitch of 20 μm without a color filter array, and good color separation and a linear response of the sensor were achieved owing to the combination of the CIS and color-selective OPFs.

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Section: Introductionsupporting

confidence: 56%

Section: Results and Discussionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Color-Filter-Free Three-Layer-Stacked Image Sensor Using Blue/Green-Selective Organic Photoconductive Films with Thin-Film Transistor Circuits on CMOS Image Sensors

Sakai¹,

Takagi²,

Imamura³

et al. 2021

ACS Appl. Electron. Mater.

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“…With the miniaturization of the sensors in recent years, the pixel size has been significantly decreased to afford a high-resolution image. However, it still remains challenging to decrease the pixel size to less than 1 μm while maintaining high sensitivity because of a decrease in the amount of photons. ,, To overcome this limitation, three-dimensional (3D) vertically stacked structures without color filters have been proposed, as the entire spectrum of visible light possibly absorbs without loss. − Among these, the stacked structures employing wavelength-selective organic photodiodes (OPDs) have been studied as promising alternatives to the conventional Si-based image sensors because of their color constancy, as the Si-based 3D-stacked structures exhibit degraded spectral characteristics. Based on this approach, the research studies successfully enhanced the spectral response and sensitivity without a loss of the active area. − We previously described organic-on-Si hybrid CMOS color image sensors, which comprised a vacuum-deposited green-light-selective OPD built onto a CMOS circuit containing a Si photodiode with R and B color filters. − Significant results including the well-balanced RGB spectra, low dark current (DC), high photoconversion efficiency, and decreased crosstalk between the pixels were achieved.…”

Section: Introductionmentioning

confidence: 99%

Green-Light-Selective Organic Photodiodes with High Detectivity for CMOS Color Image Sensors

Lim

Yun

Minami

et al. 2020

ACS Appl. Mater. Interfaces

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Stacked structures employing wavelength-selective organic photodiodes (OPDs) have been studied as promising alternatives to the conventional Si-based image sensors because of their color constancy. Herein, novel donor (D)−π–acceptor (A) molecules are designed, synthesized, and characterized as green-light-selective absorbers for application in organic-on-Si hybrid complementary metal-oxide-semiconductor (CMOS) color image sensors. The p-type molecules, combined with two fused-type heterocyclic donors and an electron-accepting unit, exhibit cyanine-like properties that are characterized by intense and sharp absorption. This molecular design leads to improved absorption properties, thermal stability, and higher photoelectric conversion compared to those of a molecular design based on a nonfused ring. A maximum external quantum efficiency of 66% (λmax = 550 nm) and high specific detectivity (D*) of 8 × 1013 cm Hz1/2/W are achieved in an OPD consisting of a bulk heterojunction blend with two transparent electrodes on both sides. Finally, the green-light-detection capability of the narrow-band green-selective OPD is demonstrated by the optical simulation of an organic-on-Si hybrid, stacked-type, full-color photodetector comprising the green-light-selective OPD and a bottom Si photodiode with only blue and red color filters. Based on this molecular design, further optimization of the OPDs can allow the development of various optoelectronic sensors including 3D-stacked image sensors with enhanced sensitivities to replace the conventional Si-based CMOS image sensors.

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High Speed Response Organic Photodetectors with Cascade Buffer Layers

Suganuma

Heo

Minami

et al. 2021

Adv Elect Materials

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the pixel size while maintaining a large effective light detection area per pixel by using a three-dimensional stacking structure. [4,5] For conventional silicon-based CISs, color filters are indispensable for the selective detection of the three primary light colors of red (R), green (G), and blue (B), because the broad absorption band of silicon exists in the wide wavelength range of 400-700 nm. Typically, CISs consist of a two-dimensional color filter array structure composed of R, G, and B pixels, i.e., a Bayer filter pattern. [6] Therefore, it is practically difficult to apply the above mentioned three dimensional stacking structure to conventional silicon based CISs.Against this background, CISs using organic materials can be a promising solution to overcome the limitations of silicon-based CISs. This is because organic materials have a narrow absorption wavelength range intrinsic to each molecule; therefore, color filters are ultimately unnecessary for selective detection of R, G, and B, making a three-dimensional stacked structure practical. Many organic dyes for high-resolution imaging devices have been developed, and it is also possible to design new organic molecules for any purpose, which is an advantage of using organic materials. [7][8][9][10] In this article, we discuss charge transfer rate enhancement in organic photodiodes (OPDs) by the minimization of energy barrier for hole transfer with cascade type hole transport layers (HTLs). Organic G sensors for hybrid CISs consisting of OPDs stacked on a silicon-based two-dimensional R and B sensors arrays, as a suboptimal concept. [11] In this organic on silicon CIS, the effective light detection area per pixel is doubled by stacking G-light sensitive OPDs on a silicon-based CMOS circuit containing R and B color filters. [12][13][14] The OPD performances have been developed to improve quantum efficiency (EQE), dark current, and thermal stability as main parameters. [15][16][17][18][19][20][21][22][23][24] High EQE contributes to higher sensitivity and higher signal to noise ratio (SNR), and less dark current stabilizes the OPD signal and yields higher SNR. Because the organic materials in OPDs are exposed to high-temperature processes, such as passivation, top layer planarization, and micro-lens forming, they should be thermally stable without degrading performance. High-speed responsivity of OPDs is also a desired specification for high-performance CISs. Recently,

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Three-layer Stacked Color Image Sensor With 2.0-μm Pixel Size Using Organic Photoconductive Film

Cited by 9 publications

References 3 publications

Color-Filter-Free Three-Layer-Stacked Image Sensor Using Blue/Green-Selective Organic Photoconductive Films with Thin-Film Transistor Circuits on CMOS Image Sensors

Color-Filter-Free Three-Layer-Stacked Image Sensor Using Blue/Green-Selective Organic Photoconductive Films with Thin-Film Transistor Circuits on CMOS Image Sensors

Green-Light-Selective Organic Photodiodes with High Detectivity for CMOS Color Image Sensors

High Speed Response Organic Photodetectors with Cascade Buffer Layers

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