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Synthesis and luminescent properties of polymer-silica multilayer-encapsulated perovskite quantum dots for optoelectronics
(1970-01-01)
Liu, Shuang-De
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
Hydrophobic all-inorganic perovskite quantum dots (IPQDs) CsPbX3 (X = Cl, Br, and I) were synthesized using conventional solution methods. IPQDs are potential materials for lasers, solar cells, and displays because of their narrow full width at half-maximum, optically tunable wavelength, and great photoluminescence quantum yield. Their shortcomings are structurally unstable and moisture sensitive. To overcome the poor stability, we have developed a chemical modification to form GQD + PMAO@SiO2 that enhances their photoluminescence quantum yield (from 60 to similar to 90%), thermal stability (from 60 to similar to 90 degrees C), and photochemical stability. The combination of the green-emitting GQD + PMAO@SiO2 and red-emitting RQD + PMAO with a 450 nm blue InGaN-based LED chip was used to fabricate a white light emitting diode with the correlated color temperature (CCT) value of 6,943 K and Commission Internationale del'Eclairage of (0.312, 0.290).
Synthesis, photoluminescence, and electroluminescence characterization of double tetraphenylethene-tethered BODIPY luminogens
(1970-01-01)
Yang, Chiun-Jen
;
Lee, Jian Haur
;
Chen, Chin-Ti
;
應用化學系
;
Department of Applied Chemistry
Three double tetraphenylethene (TPE)-tethered 4-difluoro-4-bora-3a,4a-diaza-s-indance (BODIPY) fluorophores, 35TPEBODP, 88TPEBODP, and 26TPEBODP, have been synthesized and characterized. The green 35TPEBODP with deep red fluorescence shows serious thermal decomposition in the purification process of sublimation, which prohibits its test for an organic light-emitting diode (OLED) fabricated by the vacuum-thermal evaporation process. The tethered TPE is attached to BODIPY at three different positions, resulting in different photoluminescence (emission wavelength and quantum yield) and electroluminescence (EL). Different from TPE-tethered BODIPY fluorophores reported in literature, none of the BODIPY fluorophores studied here exhibits aggregation-induced emission (AIE), aggregation-induced enhanced emission (AIEE), or twisted intramolecular charge transfer (TICT) characteristics. Although solution (10(-5) M THF) photoluminescence quantum yields (phi s) are relatively high at 78%, 68%, and 86% for 35TPEBODP, 88TPEBODP, and 26TPEBODP, respectively, which are all higher than 41% of PhBODP (a non-TPE-tethered BODIPY), the phi is significantly decreased to 1-6% in 5 wt% dopant polystyrene thin film or as a solid powder, except for 13% of 26TPEBODP. Therefore, due to the low phi of dopant thin film or solid powder, either dopant or nondopant OLEDs exhibit inferior external quantum efficiency (EQE) and intensity of EL. The best OLED in this study is the 26TPEBODP device, and its EQE reaches 1.3%, and the highest EL intensity is approximately 1,600 cd/m(2).
Improvement of perovskite photoluminescence characteristics by using a lithography-free metasurface
(2018-01-01)
Chen, Wenjun
;
Sha, Jun
;
Yan, Kanghong
;
Luo, Ji
;
Xu, Ruijia
Organic-inorganic metal halid perovskite is an emerging field of promising semiconductive material in optoelectronic devices applications. It has been a research topic of interest for scientists. To date, photoluminescence (PL) efficiency of perovskite is low and does not have any literature to report the solution. Here, we proposed and demonstrated an effective approach for the improvement of perovskite PL characteristics. The PL intensity and spectra bandwidth could be enhanced significantly by using Al-disk metasurface formed on perovskite surface. Such strategy can be exploited to enhance perovskite PL characteristics for developing high efficient light emitting diodes, solar cells, and photodetectors, etc.
Time-resolved photoluminescence of isoelectronic traps in ZnSe1-xTex semiconductor alloys
(2008-12-15)
Lin, Y. C.
;
Chou, W. C.
;
Fan, W. C.
;
Ku, J. T.
;
Ke, F. K.
Kohlrausch's stretched exponential law correlates well with the photoluminescence (PL) decay profiles of ZnSe1-xTex. As the Te concentration increases, the stretching exponent beta initially declines and then monotonically increases. This result can be understood using the hopping-transport and energy transfer model. The increase in the number of isoelectronic Te localized traps can reduce the PL decay rate and increase the linewidth, whereas the hybridization of the Te localized states with the valence-band edge states causes a reduction in both the lifetime and linewidth.
Photoluminescence-Driven Broadband Transmitting Directional Optical Nanoantennas
(2018-09-01)
See, Kel-Meng
;
Lin, Fan-Cheng
;
Chen, Tzu-Yu
;
Huang, You-Xin
;
Huang, Chen-Hsien
Optical nanoantennas mediate near and far optical fields. Operating a directional nanoantenna in transmitting mode is challenging because the antenna needs to be driven by a nanosized optical frequency generator, which must work at the antenna's resonance frequency and be precisely attached to the antenna's feed with correct polarization. Quantum emitters have been used as optical nanogenerators, but their precise positioning relative to the nanoantenna is technically challenging, setting up a barrier to the practical implementation. One unique source to drive nanoantenna is the photoluminescence from the material of the nanoantenna because the high operational frequency of the antenna reaches the regime for the electronic transitions in matter. Here, we exploit plasmon-modulated photoluminescence (PMPL) as an effective optical source to drive directional nanoantennas. We experimentally realize two technically challenging theoretical proposals, namely, an optical nanospectrometer based on Yagi-Uda nanoantennas and tunable broadband directional emission from log-periodic nanoantennas. Using photoluminescence from the nanoantenna as an optical source promotes practical implementation of transmitting optical nanoantennas.
Intrinsic Carrier Transport of Phase-Pure Homologous 2D Organolead Halide Hybrid Perovskite Single Crystals
(2018-12-27)
Li, Min-Ken
;
Chen, Tzu-Pei
;
Lin, Yen-Fu
;
Raghavan, Chinnambedu Murugesan
;
Chen, Wei-Liang
This work reveals the intrinsic carrier transport behavior of 2D organolead halide perovskites based on phase-pure homologous (n = 1, 2, and 3) Ruddelsden-Popper perovskite (RPP) (BA)(2)(MA)(n-1)PbnI3n+1 single crystals. The 2D perovskite field effect transistors with high-quality exfoliated 2D perovskite bulk crystals are fabricated, and characteristic output and transfer curves are measured from individual single-crystal flakes with various n values under different temperatures. Unipolar n-type transport dominated the electrical properties of all these 2D RPP single crystals. The transport behavior of the 2D organolead halide hybrid perovskites exhibits a strong dependence on the n value and the mobility substantially increases as the ratio of the number of inorganic perovskite slabs per organic spacer increases. By extracting the effect of contact resistances, the corrected mobility values for n = 1, 2, and 3 are 2 x 10(-3), 8.3 x 10(-2), and 1.25 cm(2) V-1 s(-1) at 77 K, respectively. Furthermore, by combining temperature-dependent electrical transport and optical measurements, it is found that the origin of the carrier mobility dependence on the phase transition for 2D organolead halide perovskites is very different from that of their 3D counterparts. Our findings offer insight into fundamental carrier transport behavior of 2D organic-inorganic hybrid perovskites based on phase-pure homologous single crystals.
Observing enhanced phosphorescence and electroluminescence from triplet emitter by quantum dot doping
(2005-01-01)
Laskar, IR
;
Liu, HW
;
Huang, CP
;
Cheng, JA
;
Chen, TM
Luminescent CdSe/ZnS core-shell-type quantum dots (QDs) were synthesized by chemical colloidal methods. The photoluminescence (PL) intensity of a triplet emitter [bis(4-trifluoromethyl)-2-phenylbenzothiazolatoacetylacetonate-iridium(III) (Ir complex 1) and bis(4-methyl)-2-phenylbenzothiazolatoacetylacetonate-iridium(III) (Ir-complex 2)] was dramatically enhanced when bluish-green emitting CdSe/ZnS QDs were incorporated into these compounds. Experimental results indicate that the emissive region of QDs substantially overlaps with the low-energy absorption bands of Ir-complexes, indicating that the photons were absorbed by both the QDs and the Ir-complexes and that the energy absorbed by the QDs was transferred efficiently to the Ir-complex triplet emitter, resulting in the observed enhancement of PL intensity. A slow quenching of QDs emission was observed in a prepared set of solutions with gradual increasing of Ir complex concentration at a fixed QDs concentration in thin film PMMA matrix, which supports the energy transfer from Ir complex to QDs. In the fabricated double-layer electroluminescent (EL) devices, the emitting layer contained either only Ir-complex or a mixture of Ir-complex and CdSe/ZnS QDs with a specific molar ratio [Ir-complex/QDs = 1/0 (D-I); 1/0.5 (D-II),..., 1/10 (D-V)]. The EL intensity and the luminance efficiency for D-II were higher (luminescence yield = 19.3cd A(-1)) than those of the other devices. The PL and EL enhancement of the triplet emitter were also strongly supported by using ZnSe QDs rather than CdSe/ZnS QDs.
Luminescent Properties and Energy Transfer of Green-Emitting Ca3Y2(Si3O9)(2):Ce3+,Tb3+ Phosphor
(2009-01-01)
Chiu, Yi-Chen
;
Liu, Wei-Ren
;
Yeh, Yao-Tsung
;
Jang, Shyue-Ming
;
Chen, Teng-Ming
Green-emitting phosphors of Ca3Y2(Si3O9)(2):Ce3+,Tb3+ have been synthesized by solid-state reaction. The luminescence properties were characterized by photoluminescence (PL) and photoluminescence excitation spectra, reflection spectra, and a detection system using an integrating sphere equipped with a spectrofluorometer. With Ce3+ co-doping as a sensitizer, the PL intensity of Ca3Y2(Si3O9)(2):Ce3+,Tb3+ was found to increase dramatically by a factor of 5.8. For comparison, the emission intensity of composition-optimized Ca3Y2(Si3O9)(2):Ce3+,Tb3+ is 126% of green commodity, ZnS:Cu,Al. The quantum efficiency of Ca3Y2(Si3O9)(2):Ce3+,Tb3+ is as high as 77% compared to ZnS:Cu,Al (53%). The energy transfer from Ce3+ to Tb3+ is also of resonant type via a dipole-dipole mechanism with the energy-transfer critical distance of 6.78 A degrees. By utilizing the principle of energy transfer and appropriate tuning of activator contents, we are currently evaluating the potential application of Ca3Y2(Si3O9)(2):Ce3+,Tb3+ as a highly efficient UV-convertible phosphor.
Spectroscopy of a single Sb2Se3 nanorod
(2009-08-01)
Sun, Kien Wen
;
Yang, Cheng-Hang
;
Ko, Ting-Yu
;
Chang, Hao-Wei
;
Liu, Chen-Wei
In this paper, we present solvothermal methods to chemically synthesize Sb2Se3 nanorods using dialkyl diselenophosphate (dsep) complexes of antimony. Energy-dispersive X-ray analysis shows the products are phase pure. We have also studied the Raman and photoluminescence spectroscopy of a single Sb2Se3 nanorod with an average size of 60 nm in diameter and a length less than 1 mu m. Techniques have been devised to immobilize and allocate a single nano-object on an electron beam (E-beam) patterned smart substrate with metallic coordination markers. This also overcomes the limitation of spatial resolution of conventional Optical techniques (similar to 1 mu m) to perform optical spectroscopy on an individual nano-object less than 100 nm in size. Raman spectroscopy reveals that Sb2Se3 nanorods synthesized at a lower temperature contain a small amount of Sb2Se3. The broad linewidth observed in luminescence spectra from a single rod is attributed to the increasing number of surface defects, impurities, and dangle bonds attached on the surface as the nanoparticle size reduced to nanometer scale.
A comprehensive study of temperature-dependent reflectance and photoluminescence of Zn1-xMnxO thin films grown on c-Al2O3
(2009-03-01)
Lin, D. Y.
;
Lin, H. J.
;
Wu, J. S.
;
Chou, W. C.
;
Yang, C. S.
We present a systematic study of temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy. For the first time, the three free-exciton transitions FXA (Gamma(7c)-Gamma(u)(7v)), FXB (Gamma(7c)-Gamma(9v)), and FXC (Gamma(7c)-Gamma(l)(7v)) and the longitudinal-optical phonon replicas of FXB and FXC of ZnMnO films have been clearly observed in the R spectra. The parameters describing the activation energy and the temperature dependence of the transition energy and broadening have been extracted by fitting the experimental R and PL spectra. The spectral data of ZnMnO films not only show the deterioration of crystalline quality with increasing Mn composition fraction but also indicate the Mn clustering caused by Mn atom segregation.

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