المؤلفون: Park, Taehyun, Lee, Dong Hyun, Hur, Jaehyun, Yoo, Hocheon

المصدر: Advanced Optical Materials; Apr2024, Vol. 12 Issue 11, p1-24, 24p

مصطلحات موضوعية: QUANTUM dots, QUANTUM confinement effects, PHOTODETECTORS, OPTICAL communications, WIRELESS communications, NITRIDES, LEAD sulfide

مستخلص: Since their discovery in 1981, quantum dots (QDs) have been the center of attention in optoelectronic fields owing to their excellent properties such as clearly discrete band structure, high luminous efficiency, and tunable energy bandgap via dot size control. Among them, the bandgap increase characteristic based on the quantum confinement effect opens a new horizon in the field of deep ultraviolet photodetectors (DUV PDs). Emerging applications such as risk monitoring, wireless optical communication, and chemical sensing with extremely low environmental interference raise the significance of DUV PDs. Nonetheless, the limited material selection for DUV absorption has been the main obstacle for further applications. Along this line, this review systematically revisits the recent advances in QD‐based DUV PDs, using bandgap‐widened QDs, with a focus on the synthetic method, device architecture, and interactions among constituent components. Various QDs categorized into carbon, oxide, sulfide, and nitride are reviewed with the specific characteristics of each substance. The future prospects of QD‐based DUV PDs in terms of practical applications and the current challenges are discussed. [ABSTRACT FROM AUTHOR]

: Copyright of Advanced Optical Materials is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Shin, Jihyun¹ (AUTHOR), Yoo, Hocheon¹ (AUTHOR) hyoo@gachon.ac.kr

المصدر: Nanomaterials (2079-4991). Mar2023, Vol. 13 Issue 5, p882. 21p.

مصطلحات موضوعية: *PHOTODETECTORS, *PHOTOELECTRIC effect, *POTENTIAL energy, *THRESHOLD voltage, *DIELECTRICS

مستخلص: Rather than generating a photocurrent through photo-excited carriers by the photoelectric effect, the photogating effect enables us to detect sub-bandgap rays. The photogating effect is caused by trapped photo-induced charges that modulate the potential energy of the semiconductor/dielectric interface, where these trapped charges contribute an additional electrical gating-field, resulting in a shift in the threshold voltage. This approach clearly separates the drain current in dark versus bright exposures. In this review, we discuss the photogating effect-driven photodetectors with respect to emerging optoelectrical materials, device structures, and mechanisms. Representative examples that reported the photogating effect-based sub-bandgap photodetection are revisited. Furthermore, emerging applications using these photogating effects are highlighted. The potential and challenging aspects of next-generation photodetector devices are presented with an emphasis on the photogating effect. [ABSTRACT FROM AUTHOR]

المؤلفون: Woo, Gunhoo, Kim, Taesung, Yoo, Hocheon

المصدر: Advanced Electronic Materials; Feb2023, Vol. 9 Issue 2, p1-17, 17p

مصطلحات موضوعية: METAL oxide semiconductor field-effect transistors, TUNNEL field-effect transistors, TUNNEL design & construction, FIELD-effect transistors, ELECTRIC fields

مستخلص: Band‐to‐band tunneling (BTBT) devices with superior subthreshold swing directly related to on/off switching speed and power consumption efficiency have emerged as a breakthrough of the limitation in conventional metal‐oxide‐semiconductor field‐effect transistors (MOSFETs). However, it is difficult to reach a higher level of electrical characteristics with only a combination of materials based on their intrinsic characteristics. External forces, such as electric fields, light, and temperature, can modulate the electron and hole concentration and control the tunneling probability and the electrical characteristics of heterostructure electronics. Recent articles employing external forces to improve the BTBT performance and demonstrate the mechanism of BTBT devices are summarized with five representative external forces. Moreover, the utility of the external force‐induced performance improvement of the BTBT device is also discussed by providing various applications. [ABSTRACT FROM AUTHOR]

: Copyright of Advanced Electronic Materials is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Seo, Juhyung, Kim, Yeong Jae, Yoo, Hocheon

المصدر: Micromachines; Dec2022, Vol. 13 Issue 12, p2089, 18p

مصطلحات موضوعية: PHOTODETECTORS, ENERGY bands, ELECTRIC fields, DETECTORS

مستخلص: Zero-biased photodetectors have desirable characteristics for potentially next-generation devices, including high efficiency, rapid response, and low power operation. In particular, the detector efficiency can be improved simply by changing the electrode contact geometry or morphological structure of materials, which give unique properties such as energy band bending, photo absorbance and electric field distribution. In addition, several combinations of materials enable or disable the operation of selective wavelengths of light detection. Herein, such recent progresses in photodetector operating at zero-bias voltage are reviewed. Considering the advantages and promises of these low-power photodetectors, this review introduces various zero-bias implementations and reviews the key points. [ABSTRACT FROM AUTHOR]

: Copyright of Micromachines is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Park, Taehyun, Kim, Daekwan, Shin, Bongguen, Hur, Jaehyun, Yoo, Hocheon

المصدر: Advanced Optical Materials; Apr2022, Vol. 10 Issue 7, p1-10, 10p

مصطلحات موضوعية: PHOTODETECTORS, EMERGENCY medical services, ULTRAVIOLET radiation, TIN oxides

مستخلص: A rapid and efficient opto‐electrical method for the determination of blood components is demonstrated through a tin oxide (SnO2) quantum dot (QD) fluorene copolymer heterojunction photodetector (FP‐PD). The photo‐active materials, the device structure, and the sensing system are carefully designed to provide miniaturization at a low cost. SnO2 QDs are synthesized with a one‐step solvothermal reaction and a photodetector, and then fabricated in a simple sequential spin‐coating process. Under optimal conditions, the SnO2 QD/FP‐PD shows remarkable responsivity, detectability, fast responses, and stability under self‐powered operation. In this research, optical characteristics of blood components, and interactions between the photodetector and blood components from illuminating two different wavelengths of ultraviolet light, are systemically investigated. Furthermore, three different blood component mixtures are successfully determined by the SnO2 QD/FP‐PD based on specific absorption phenomena, which provides a simple and efficient technique for emergency medical care and health monitoring systems. [ABSTRACT FROM AUTHOR]

: Copyright of Advanced Optical Materials is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Ko, Kyungil¹ (AUTHOR), Park, Taehyun¹ (AUTHOR), Yoo, Hocheon^1,2 (AUTHOR) hyoo@gachon.ac.kr, Hur, Jaehyun¹ (AUTHOR) jhhur@gachon.ac.kr

المصدر: Journal of Alloys & Compounds. Dec2023, Vol. 969, pN.PAG-N.PAG. 1p.

مصطلحات موضوعية: *PHOTODETECTORS, *SCHOTTKY barrier, *POLYMER electrodes, *NAFION, *DOPING agents (Chemistry), *THERMAL stability

مستخلص: Deep-ultraviolet (DUV) photodetectors (PDs) are gaining significant importance in applications such as ultraviolet communication, monitoring, and missile detection. MgTiO 3 (MTO) has demonstrated exceptional suitability for DUV PDs owing to its extensive UVC light detection ability in the superwide band (4.4–4.6 eV) and its structural and thermal stability. In this study, we fabricated a semi-transparent MTO-based self-powered vertical metal-semiconductor-metal PD using a facile solution process. Two different transparent electrodes (ITO and PEDOT:PSS) in contact with the MTO semiconductor allowed not only self-powered operation but also high transparency of the PD. The thickness of the MTO film was controlled to increase the depletion width at the semiconductor–electrode junction. In addition, the work function of the PEDOT:PSS was modulated by adding Nafion. At appropriate conditions of MTO film thickness and Nafion doping concentration in PEDOT:PSS, the device exhibited high responsivity (4.06 mA W−1) and detectivity (3.76 ×109 Jones), fast response time (303/608 ms for rise/decay time), and good stability (over 100 cycles of on–off operations) under UVC light illumination. This study provides new insights into the cost-effective fabrication of high-performance semi-transparent DUV PD. [Display omitted] • Solution processed MgTiO 3 -based vertical MSM PD is fabricated. • MgTiO 3 film thickness affects the number of photocarriers of the PD. • Nafion added in PEDOT:PSS can modulate the Schottky barrier height for the PD. • Asymmetric Schottky junctions enables self-powered operation of the PD. • Semi-transparent MgTiO 3 -based MSM PD exhibits good responsivity and response time. [ABSTRACT FROM AUTHOR]

المؤلفون: Park, Eunhee¹ (AUTHOR), Park, Taehyun¹ (AUTHOR), Yoo, Hocheon^1,2 (AUTHOR) hyoo@gachon.ac.kr, Hur, Jaehyun¹ (AUTHOR) jhhur@gachon.ac.kr

المصدر: Journal of Alloys & Compounds. Oct2022, Vol. 918, pN.PAG-N.PAG. 1p.

مصطلحات موضوعية: *QUANTUM dots, *PHOTODETECTORS, *CARBAZOLE, *HETEROJUNCTIONS, *ENVIRONMENTAL monitoring

مستخلص: Ultraviolet C (UVC) photodetectors have attracted significant attention recently owing to the importance of UVC detection for preventing human skin damage, monitoring environmental conditions, detecting power facility aging, and military applications. The "solar-blindness" of UVC detectors ensures low noise levels, benefiting from lower interference than other environmental signals. In this study, a solution-processed PN heterojunction consisting of P-type polymer (poly(9-vinyl carbazole) (PVK)) and N-type metal oxide quantum dots (SnO 2 QDs) was used to develop a self-powered high-performance UVC photodetector. Reducing the size of the SnO 2 QDs significantly enhanced the selective absorption of the UVC wavelength range via quantum confinement. The device architecture and constituent film thickness were carefully controlled to enhance the performance of the PVK/SnO 2 QD UVC photodetector. Under the optimized conditions, the device exhibited remarkable responsivity (49.6 mA W−1 at 254 nm and 166 mA W−1 at 220 nm), detectivity (2.16 × 1010 Jones at 254 nm), UVC/ultraviolet A (UVA) rejection ratio (R 254 nm /R 365 nm and R 220 nm /R 365 nm of ~260 and 880, respectively), and stability over long-term self-powered on/off operations. Our solar-blind UVC photodetector can be used to inexpensively, simply, and precisely monitor hazardous UVC light in various applications. [Display omitted] • Solution processed PVK/SnO2 QD photodetector was fabricated for UVC detection. • Effect of device structure (PN vs NP) on the UVC sensing performance was studied. • PVK and SnO2 QD layer thicknesses were optimized to enhance sensing performance. • PVK/SnO2 QD displayed superb photoresponse, detectivity, and stability. [ABSTRACT FROM AUTHOR]