Lanthanide-based luminescent hybrid materials.

Global environmental concerns and the escalating demand for energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till date. The power from sun intercepted by the earth is about 1.8 × 1011 MW, which is many times larger than the present rate of all the energy consumption. Photovoltaic technology is one of the finest ways to harness the solar power. This paper reviews the photovoltaic technology, its power generating capability, the different existing light absorbing materials used, its environmental aspect coupled with a variety of its applications. The different existing performance and reliability evaluation models, sizing and control, grid connection and distribution have also been discussed. © 2011 Published by Elsevier Ltd.

A review of solar photovoltaic technologies

The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1) and triplet (T1) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1→S1) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

We thank the University of St Andrews for support. EZ-C thanks the Leverhulme Trust for financial support (RPG-2016-047). and the EPSRC (EP/P010482/1) for financial support.

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Purely Organic Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes.

Recently, the use of phosphorescent heavy-metal complexes as chemosensors has attracted increasing interest due to their advantageous photophysical properties. This critical review focuses on the design principles and the recent development of phosphorescent chemosensors for metal cations, anions, pH, oxygen, volatile organic compounds and biomolecules based on some heavy-metal complexes (such as Pt(II)-, Ru(II)-, Re(I)-, Ir(III)-, Cu(I)-, Au(I)- and Os(II)-based complexes), in which the variation in phosphorescence signals induced by the interaction between heavy-metal complexes and analytes is utilized (217 references).

Phosphorescent chemosensors based on heavy-metal complexes

We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4',4 ''-tris[3-methylphenyl(phenyl)-aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm(2) was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process.

Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a ΔES-T of around zero.

Quantitative understanding of the photophysical processes is essential for developing novel thermally activated delayed fluorescence (TADF) materials Taking as an example 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene, a typical TADF-active molecule, we calculated the interconversion and decay rates of the lowest excited singlet and triplet states at different temperatures as well as the prompt and delayed fluorescence efficiencies at 300 K at the first-principles level Our results can reproduce well the experimentally available data It is found that the reverse intersystem crossing rate (kRISC) is sharply increased by 3 orders of magnitude, while the other rates increase slightly or remain unchanged when the temperature rises from 77 to 300 K Importantly, kRISC reaches up to 123 × 106 s–1 and can compete with the radiative and nonradiative decay rates of S1 (111 × 107 and 237 × 105 s–1) at 300 K, leading to an occurrence of delayed fluorescence In addition, our calculations indicate that it i

Theoretical Study of Conversion and Decay Processes of Excited Triplet and Singlet States in a Thermally Activated Delayed Fluorescence Molecule

Nanocrystalline ZrO2 fine powders were prepared via the one-pot reaction followed by annealing from 700 to 1100 °C in air. It is believed that generation of excess oxygen vacancies within nanocrystalline ZrO2 is primarily responsible for room-temperature tetragonal phase stabilization below a critical size, and the phase transformation from tetragonal to monoclinic ZrO2 happened in the annealing process. Luminescent properties of ZrO2 were greatly affected by oxygen vacancies in the phase transition process. Two bands centered at 350 and 470 nm were observed in tetragonal ZrO2. The electrons trapped by oxygen vacancies creating F centers recombined with holes yielding the 350 nm luminescence. Temporal decay of the 470 nm luminescence is due to the detrapping of electrons to the Ti3+ luminescence centers. Elevated temperature accelerated the phase transformation to monoclinic ZrO2 and decreased the oxygen vacancy concentration, resulting in a decrease of the 350 nm emission and enhancement of the 470 nm ph...

http://bec01.phy.georgiasouthern.edu/xwang/research/JPCC%20Cong%20Yan2%2009.pdf

Effect of Oxygen Vacancy on Phase Transition and Photoluminescence Properties of Nanocrystalline Zirconia Synthesized by the One-Pot Reaction

A series of [Cu(N–N)(P–P)]BF4 complexes: Luminescence quenching caused by electron-configuration transformation in excited state

A novel copper(I) complex [Cu(POP)(PTZ)]BF4 (POP = bis[2-(diphenyl-phosphino)phenyl]-ether, PTZ = 5-(2-pyridyl)tetrazole) has been synthesized and characterized by elemental analysis, 1H NMR and IR. Complex [Cu(POP)(PTZ)]BF4 shows bright bluish-green emission centered at 495 nm in solid-state at room temperature, arising from metal to ligand charge-transfer (MLCT) transition. The photoluminescence quantum yield measured in air is 0.12. The excited state lifetime of [Cu(POP)(PTZ)]BF4 is on the order of microsecond indicating the presence of phosphorescent emission. The emission intensity of [Cu(POP)(PTZ)]BF4 appears to be highly sensitive to the O2 concentration, meaning it possesses oxygen-sensing property. The sensing performances of [Cu(POP)(PTZ)]BF4/MCM-41 composite materials are evaluated and the system with 20 mg/g loading level exhibits the best sensitivity (I0/I100 > 11), and the shortest response time (t↓

Di Fan

Papers

Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a ΔES-T of around zero.

Theoretical Study of Conversion and Decay Processes of Excited Triplet and Singlet States in a Thermally Activated Delayed Fluorescence Molecule

Effect of Oxygen Vacancy on Phase Transition and Photoluminescence Properties of Nanocrystalline Zirconia Synthesized by the One-Pot Reaction

A series of [Cu(N–N)(P–P)]BF4 complexes: Luminescence quenching caused by electron-configuration transformation in excited state

Synthesis, photophysical and oxygen-sensing properties of a novel bluish-green emission Cu(I) complex