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A skin-like two-dimensionally pixelized full-color quantum dot photodetector

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Science Advances  22 Nov 2019:
Vol. 5, no. 11, eaax8801
DOI: 10.1126/sciadv.aax8801
  • Fig. 1 Schematic of the device structure of the QD/AOS hybrid phototransistor.

    (A) A schematic three-dimensional view of a phototransistor array. (B) Optical absorption of QDs used to fabricate the full-color detectors. (C) PbS QDs (10 nm diameter), CdSe QDs (7 nm diameter), CdSe QDs (5 nm diameter), and CdS QDs (3 nm diameter) absorb IR, red, green, and blue, respectively. (D) Three-dimensional impression image of phototransistor and (E and F) corresponding cross-sectional HRTEM images. Scale bars, 50 nm (E) and 5 nm (F). a.u., arbitrary units. Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

  • Fig. 2 Interfacial properties between QDs and the AOS channel layer.

    (A and B) Noise power spectral density of 7-nm CdSe QD/a-IGZO with SCN and Sn2S64− ligand phototransistors. (C and D) Scanning photocurrent imaging (0 V source per drain bias) of the QD/a-IGZO phototransistor with Sn2S64− and SCN ligands. Scale bars, 5 μm. (E and F) Photocurrent profile with a laser wavelength of 532 nm and a power of 0.45 μW from along the blue dashed line in (C) and (D). Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

  • Fig. 3 Optoelectronic performance of the QD/AOS hybrid phototransistor.

    Photoresponse characteristics of the QD/a-IGZO phototransistor with (A) Sn2S64− and (B) SCN ligands. (C) Photosensitivity (R) and (D) photodetectivity (D*) under white light (1.36 mW cm−2) and broadband illumination (inset). Light intensities of UV, blue, green, and red are 1 mW cm−2, while that for IR is 13.6 mW cm−2 and that for white light is 1.36 mW cm−2. (E) EQE and (F) dynamic range of 7-nm CdSe QD/a-IGZO with the Sn2S64− ligand (blue line) and the SCN ligand (red line) phototransistor. Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

  • Fig. 4 Fine-patterned QDs characteristics.

    (A) Schematic representation of QDs to design photosensitive inorganic ligands. (B) Optical and (C) field-enhanced scanning electron microscopy (FESEM) images of patterned CdSe QDs capped with Sn2S64− ligands. (D) CdS QDs, (E) PbS QDs. Scale bars, 100 μm (B), 5 μm (C), 20 μm (D), and 10 μm (E). (F and G) Atomic force microscopy (AFM) scan image and height profile of CdSe QDs from along the blue dashed line. Scale bar, 5 μm. Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

  • Fig. 5 CIC array characteristics for full-color discrimination.

    (A) Schematic diagram of CIC and logic table of full-color signal detection in one pixel. (B) Optical micrograph of the partially patterned QDs including IR PbS (T1, 10 nm), red CdSe (T2, 7 nm), green CdSe (T3, 5 nm), and blue CdS (T4, 3 nm) and bare a-IGZO phototransistors and the schematic of amplification circuit. RTN is the channel resistance of load TFTs (T1 to T4), and RT6 is the channel resistance of driver TFT (T6). Here, channel width/length are 100/50 μm (load TFTs), 200/10 μm (T5), and 5/200 μm (T6). Scale bar, 50 μm. (C to G) Photoresponse characteristics of T1, T2, T3, T4, and T5/T6 with respect to wavelength of light. (H) Output current of the five-channel full-color photodetector. (I) Mixed light discrimination. Light intensities of UV, blue, green, and red are 1 mW cm−2, while that for IR is 13.6 mW cm−2. For yellow, red (0.5 mW cm−2) and green (0.5 mW cm−2) were mixed, and for cyan, green (0.5 mW cm−2) and blue (0.5 mW cm−2) were mixed. Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

  • Fig. 6 Full-color two-dimensional mapping applications.

    (A) Schematic illustration of the 10 by 10 CIC array. (B) Optical micrograph of the 10 by 10 CIC array on an ultrathin PI substrate and the associated circuit schematic (right). Scale bars, 1 mm and 300 μm (inset). (C) Relevant intensity profile reconstructed from output current mapping of the 10 by 10 CIC array on an ultrathin PI substrate with respect to the wavelength of light [IR (1310 nm), R (638 nm), G (520 nm), B (406 nm), and UV (365 nm)]. Light intensities of UV, blue, green, and red are 1 mW cm−2, while that for IR is 13.6 mW cm−2. Scale bar, 3 mm. (D) Round and stripe shape two-dimensional mapping images with white light illumination (halogen lamp with 1.36 mW cm−2). Scale bar, 3 mm. (E) Photograph of band-type flexible health monitoring system composed of four light sources and phototransistor-based circuit arrays (CIC) attached onto an index fingertip. (F) Full-color two-dimensional biological mapping images of human fingertip with respect to the wavelength of light. Light intensities of blue, green, and red are 3 mW cm−2, while that for IR is 13.6 mW cm−2. Each light is placed on the subject’s finger, and the transmitted light is collected with the phototransistor-based CIC array placed below the finger. Photo credit: Jaehyun Kim, Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06974, Korea.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaax8801/DC1

    Fig. S1. Colloidal QD solutions.

    Fig. S2. Electrical characteristics of low-temperature photoactivated sol-gel a-IGZO TFTs.

    Fig. S3. Absorption spectra of a-IGZO film.

    Fig. S4. Synthesis and chemical analysis for chelating chalcometallate ligands (Sn2S64−).

    Fig. S5. Optoelectronic mechanism of a QD phototransistor.

    Fig. S6. SPCM analysis for a QD phototransistor.

    Fig. S7. SPCM analysis for an a-IGZO phototransistor.

    Fig. S8. Optoelectrical characteristics of a-IGZO TFT and oleic acid-QD/a-IGZO phototransistors.

    Fig. S9. Photodetectivity (D*) of a QD/a-IGZO phototransistor with Sn2S64− and SCN ligands as a function of the frequency.

    Fig. S10. Photoswitching properties of CdSe QD/a-IGZO phototransistors.

    Fig. S11. Temporal response of CdSe QD/a-IGZO phototransistors.

    Fig. S12. Temporal photocurrent response of CdSe QD/a-IGZO phototransistors.

    Fig. S13. Absorption spectra of chelating chalcometallate ligands.

    Fig. S14. Optoelectrical characteristics of CdSe QD/a-IGZO phototransistors before and after QDs patterning.

    Fig. S15. Examples of optically patterned QDs.

    Fig. S16. HRTEM images of the QDs.

    Fig. S17. XPS analysis of CdSe QDs.

    Fig. S18. Schematic of direct photolithography process for fine-patterned diverse QD layers.

    Fig. S19. In-pixel charge integrating and amplification circuit analysis.

    Fig. S20. Limitation of color discrimination of a single phototransistor without a CIC circuit.

    Fig. S21. Discrimination of various light wavelength from mixed light.

    Fig. S22. Five-channel QD/a-IGZO phototransistors composed of CIC pixel with glass and PI substrate.

    Fig. S23. Full-color two-dimensional biological mapping images.

    Fig. S24. Long-term reliability test for CdSe QD/a-IGZO with a Sn2S64− ligand phototransistor.

    Fig. S25. Ultraflexibility of phototransistor.

    Fig. S26. In situ mechanical (bending and cycling) tests for conformal full-color photodetector arrays.

    Fig. S27. Photoresponse characteristics of ultraflexible phototransistors.

    Fig. S28. Photoresponse characteristics of ultraflexible phototransistors.

    References (4144)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Colloidal QD solutions.
    • Fig. S2. Electrical characteristics of low-temperature photoactivated sol-gel a-IGZO TFTs.
    • Fig. S3. Absorption spectra of a-IGZO film.
    • Fig. S4. Synthesis and chemical analysis for chelating chalcometallate ligands (Sn2S64−).
    • Fig. S5. Optoelectronic mechanism of a QD phototransistor.
    • Fig. S6. SPCM analysis for a QD phototransistor.
    • Fig. S7. SPCM analysis for an a-IGZO phototransistor.
    • Fig. S8. Optoelectrical characteristics of a-IGZO TFT and oleic acid-QD/a-IGZO phototransistors.
    • Fig. S9. Photodetectivity (D*) of a QD/a-IGZO phototransistor with Sn2S64− and SCN ligands as a function of the frequency.
    • Fig. S10. Photoswitching properties of CdSe QD/a-IGZO phototransistors.
    • Fig. S11. Temporal response of CdSe QD/a-IGZO phototransistors.
    • Fig. S12. Temporal photocurrent response of CdSe QD/a-IGZO phototransistors.
    • Fig. S13. Absorption spectra of chelating chalcometallate ligands.
    • Fig. S14. Optoelectrical characteristics of CdSe QD/a-IGZO phototransistors before and after QDs patterning.
    • Fig. S15. Examples of optically patterned QDs.
    • Fig. S16. HRTEM images of the QDs.
    • Fig. S17. XPS analysis of CdSe QDs.
    • Fig. S18. Schematic of direct photolithography process for fine-patterned diverse QD layers.
    • Fig. S19. In-pixel charge integrating and amplification circuit analysis.
    • Fig. S20. Limitation of color discrimination of a single phototransistor without a CIC circuit.
    • Fig. S21. Discrimination of various light wavelength from mixed light.
    • Fig. S22. Five-channel QD/a-IGZO phototransistors composed of CIC pixel with glass and PI substrate.
    • Fig. S23. Full-color two-dimensional biological mapping images.
    • Fig. S24. Long-term reliability test for CdSe QD/a-IGZO with a Sn2S64− ligand phototransistor.
    • Fig. S25. Ultraflexibility of phototransistor.
    • Fig. S26. In situ mechanical (bending and cycling) tests for conformal full-color photodetector arrays.
    • Fig. S27. Photoresponse characteristics of ultraflexible phototransistors.
    • Fig. S28. Photoresponse characteristics of ultraflexible phototransistors.
    • References (4144)

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