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Yan S. Negative Thermal Quenching of Photoluminescence: An Evaluation from the Macroscopic Viewpoint. MATERIALS (BASEL, SWITZERLAND) 2024; 17:586. [PMID: 38591414 PMCID: PMC10856741 DOI: 10.3390/ma17030586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 01/13/2024] [Accepted: 01/19/2024] [Indexed: 04/10/2024]
Abstract
Negative thermal quenching (NTQ) denotes that the integral emission spectral intensity of a given phosphor increases continuously with increasing temperature up to a certain elevated temperature. NTQ has been the subject of intensive investigations in recent years, and a large number of phosphors are reported to have exhibited NTQ. In this paper, a collection of results in the archival literature about NTQ of specific phosphors is discussed from a macroscopic viewpoint, focusing on the following three aspects: (1) Could the NTQ of a given phosphor be reproducible? (2) Could the associated data for a given phosphor exhibiting NTQ be in line with the law of the conservation of energy? (3) Could the NTQ of a given phosphor be demonstrated in a prototype WLED device? By analyzing typical cases based on common sense, we hope to increase awareness of the issues with papers reporting the NTQ of specific phosphors based on spectral intensity, along with the importance of maintaining stable and consistent measurement conditions in temperature-dependent spectral intensity measurement, which is a prerequisite for the validity of the measurement results.
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Affiliation(s)
- Shirun Yan
- Department of Chemistry, Fudan University, Shanghai 200438, China
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2
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Träger LM, Pasqualini LC, Huppertz H, Bruns J, Suta M. Photoluminescence of Mn 2+ in the Borosulfate Zn[B 2 (SO 4 ) 4 ] : Mn 2+ -A Tool to Detect Weak Coordination Behavior of Ligands. Angew Chem Int Ed Engl 2023; 62:e202309212. [PMID: 37548647 DOI: 10.1002/anie.202309212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/08/2023]
Abstract
The impact of the surrounding ligand field is successfully exploited in the case of Eu2+ to tune the emission characteristics of inorganic photoactive materials with potential application in, e.g., phosphor-converted white light-emitting diodes (pc-wLEDs). However, the photoluminescence of Mn2+ related to intraconfigurational 3d5 -3d5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal-ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer-like borosulfate ligand in the Mn2+ -containing solid solutions Zn1-x Mnx [B2 (SO4 )4 ] (x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B2 (SO4 )4 ]:Mn2+ shows orange narrow-band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn-O bonds with values close to the Racah parameters of the free Mn2+ ion. Overall, this strategy demonstrates that electronic control of the metal-ligand bond can be a tool to make Mn2+ a potent alternative emitter to Eu2+ for inorganic phosphors.
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Affiliation(s)
- Lukas M Träger
- Inorganic Photoactive Materials, Institute of Inorganic Chemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Leonard C Pasqualini
- Institute of General, Inorganic, and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, Innsbruck, 6020, Austria
| | - Hubert Huppertz
- Institute of General, Inorganic, and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, Innsbruck, 6020, Austria
| | - Jörn Bruns
- Institute of Inorganic Chemistry, University of Cologne, Greinstrasse 6, 50939, Cologne, Germany
| | - Markus Suta
- Inorganic Photoactive Materials, Institute of Inorganic Chemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
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3
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Srivastava S, Lee KE, Fitzgerald EA, Pennycook SJ, Gradečak S. Freestanding High-Resolution Quantum Dot Color Converters with Small Pixel Sizes. ACS APPLIED MATERIALS & INTERFACES 2022; 14:48995-49002. [PMID: 36274221 DOI: 10.1021/acsami.2c14212] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Designing the next generation of high-resolution displays requires high pixel density per area and small pixel sizes without compromising the optical quality. Quantum dots (QDs) have been demonstrated as a promising material system for down-conversion of blue emission as they provide pure colors on the wide color gamut. However, for high color-conversion efficiency, the required QD film thickness has not been compatible with small pixel sizes. In this work, we develop a new type of freestanding QD-based color converter for efficient optical down-conversion from inorganic blue light-emitting diodes (LEDs) in a color-by-blue configuration. CdSe/ZnS core-shell QDs in a UV-curable polymer matrix are encapsulated within cavities formed by patterning and bonding a pair of patterned quartz substrates. By controlling the required QD thickness and the pixel size independently, we demonstrate freestanding monochrome red and green converters with small pixel sizes down to 5 × 5 μm2 and a high resolution of >3600 ppi. The optical studies show that the QD film thickness required for efficient color conversion can be successfully realized even for the small pixel sizes. We further combine green and red pixels in a single converter to achieve white emission when combined with blue LED emission. The QD color converter design and processing are decoupled from the LED fabrication and can be easily scaled to wafer-size integration with arbitrary pixel sizes for QD-based RGB displays with ultrahigh resolution.
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Affiliation(s)
- Saurabh Srivastava
- Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, 138602 Singapore
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, 138634 Singapore
| | - Kenneth E Lee
- Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, 138602 Singapore
| | - Eugene A Fitzgerald
- Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, 138602 Singapore
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02141, United States
| | - Stephen J Pennycook
- Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, 138602 Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
| | - Silvija Gradečak
- Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, 138602 Singapore
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02141, United States
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
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Li G, Liu Y, Xu Q, Liang H, Wang X. Deep learning enabled inverse design of nanocrystal-based optical diffusers for efficient white LED lighting. APPLIED OPTICS 2022; 61:8783-8791. [PMID: 36256012 DOI: 10.1364/ao.471243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/20/2022] [Indexed: 06/16/2023]
Abstract
Angular color uniformity and luminous flux are the most important figures of merit for a white-light-emitting diode (WLED), and simultaneous improvement of both figures of merit is desired. The cellulose-nanocrystal (CNC)-based optical diffuser has been applied on the WLED module to enhance angular color uniformity, but it inevitably causes the reduction of luminous flux. Here we demonstrate a deep-learning-based inverse design approach to design CNC-coated WLED modules. The developed forward neural network successfully predicts two figures of merit with high accuracy, and the inverse predicting model can rapidly design the structural parameters of CNC film. Further explorations taking advantage of both forward and inverse neutral networks can effectively construct the coating layer for WLED modules to reach the best performance.
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van Swieten T, Meijerink A, Rabouw FT. Impact of Noise and Background on Measurement Uncertainties in Luminescence Thermometry. ACS PHOTONICS 2022; 9:1366-1374. [PMID: 35480490 PMCID: PMC9026254 DOI: 10.1021/acsphotonics.2c00039] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Indexed: 05/03/2023]
Abstract
Materials with temperature-dependent luminescence can be used as local thermometers when incorporated in, for example, a biological environment or chemical reactor. Researchers have continuously developed new materials aiming for the highest sensitivity of luminescence to temperature. Although the comparison of luminescent materials based on their temperature sensitivity is convenient, this parameter gives an incomplete description of the potential performance of the materials in applications. Here, we demonstrate how the precision of a temperature measurement with luminescent nanocrystals depends not only on the temperature sensitivity of the nanocrystals but also on their luminescence strength compared to measurement noise and background signal. After first determining the noise characteristics of our instrumentation, we show how the uncertainty of a temperature measurement can be predicted quantitatively. Our predictions match the temperature uncertainties that we extract from repeated measurements, over a wide temperature range (303-473 K), for different CCD readout settings, and for different background levels. The work presented here is the first study that incorporates all of these practical issues to accurately calculate the uncertainty of luminescent nanothermometers. This method will be important for the optimization and development of luminescent nanothermometers.
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Abe A, Goushi K, Sandanayaka ASD, Komatsu R, Fujihara T, Mamada M, Adachi C. Numerical Study of Triplet Dynamics in Organic Semiconductors Aimed for the Active Utilization of Triplets by TADF under Continuous-Wave Lasing. J Phys Chem Lett 2022; 13:1323-1329. [PMID: 35107294 DOI: 10.1021/acs.jpclett.1c03983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The limitation of lasing duration less than nanosecond order has been a major problem for realizing organic solid-state continues-wave (CW) lasers and organic semiconductor laser diodes. Triplets accumulation under CW excitation has been well recognized as a critical inhibiting factor. To overcome this issue, the utilization of thermally activated delayed fluorescence (TADF) emitters is a promising mechanism because of efficient reverse intersystem crossing. Herein, we model the triplet accumulation processes under lasing and propose the active utilization of TADF for lasing based on our simulation analysis. We used the rate constants experimentally determined from the optical properties of a boron difluoride curcuminoid fluorophore showing both TADF and lasing. We demonstrate that the intersystem crossing efficiency is gradually increased after the convergence of relaxation oscillation, i.e., terminating laser oscillation. In addition, we found that when the reverse intersystem crossing rate is close to the intersystem crossing rate, CW lasing becomes dominant.
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Affiliation(s)
- Ayano Abe
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Kenichi Goushi
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- International Institute for Carbon Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | | | - Ryutaro Komatsu
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Takashi Fujihara
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Masashi Mamada
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Chihaya Adachi
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- International Institute for Carbon Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
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7
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Tyagi A, Nigam S, Vats BG, Sudarsan V, Majumder C, Kaiwart R, Poswal HK, Jagannath, Tyagi AK. Revealing Eu 3+-doped yttrium pyrogermanate as a soft UV excitable phosphor: retaining the pros of the commercial phosphor and compensating for the cons. NEW J CHEM 2022. [DOI: 10.1039/d2nj03374g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article presents the synthesis of a single-phase red emitting Y2Ge2O7:Eu3+ soft-UV excitable phosphor with up to 10% Eu3+ content. Experimental and theoretical exploration has established its relative potential with respect to the commercial Y2O3:Eu3+ phosphor.
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Affiliation(s)
- Adish Tyagi
- Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
| | - Sandeep Nigam
- Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
| | - B. G. Vats
- Fuel Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
| | - V. Sudarsan
- Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
| | - C. Majumder
- Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
| | - R. Kaiwart
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
- High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
| | - H. K. Poswal
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
- High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
| | - Jagannath
- Technical Physics Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
| | - A. K. Tyagi
- Chemistry Division, Bhabha Atomic Research Center, Mumbai, 400 085, India
- Homi Bhabha National Institute (HBNI), Mumbai, 400 094, India
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