Genetic algorithm-assisted combinatorial chemistry (GACC) was implemented to search for new blue phosphors in seven cation systems, including CaO, MgO, BaO, SrO, B 2 O 3 , P 2 O 5 , and Eu 2 O 3 . The GACC process was followed by a series of fine-tuning processes based on conventional high-throughput screening employing quaternary and ternary libraries, to pinpoint promising compositions. GACC was found to be useful as a preliminary step for final screening. This series of processes involving computations and actual syntheses led us to (Sr 1-x-y Ca x Ba y ) 2 P 2 O 7 :Eu 2+ (0.32 < x < 0.72, y < 0.04) phosphors. It was found that the boron addition played a significant role in enhancing the luminance but it was completely evaporated during the synthesis, and an excessive amount of alkali earth elements was essential for better luminescence. The luminance of (Sr 1-x-y Ca x Ba y ) 2 P 2 O 7 :Eu 2+ (0.32 < x < 0.72, y < 0.04) phosphors reached 70% of a commercially available BAM phosphor at 254 nm excitation. The color chromaticity was in the deep blue region, x ) 0.15, y ) 0.05. The structure of these phosphors was found to be Sr 2 P 2 O 7 (Pnma, 62), but the luminescent property was far better than the Sr 2 P 2 O 7 :Eu 2+ phosphor.

We examined the photoluminescent behaviors of MgSiN2:Mn2+ and MgSiN2:Ce3+,Mn2+ phosphors for use in white-light-emitting diodes. The red emission from MgSiN2:Mn2+ phosphors consisted of two Gaussian components, P1 from a single Mn2+ ion and P2 from either Mn2+ pairs or clusters. Decay analysis based on the Yokota and Tanimoto equation identified long decay for P1 and fast decay for P2. Most importantly, Ce3+ codoping enhanced Mn2+ emission intensity; in particular, emission at 460 nm excitations was promoted by the Ce3+ codoping.

The baricenter and crystal field splitting of the 5d transition of the Eu 2+ activator were approximated from the experimental spectrum data for Li 2 SrSiO 4 , Li 2 CaSiO 4 , and Li 2 BaSiO 4 hosts and examined in conjunction with the ionic radii of neighboring alkali earth ions and the local structure around the divalent europium activator. In addition, Li 2 ͑Sr,Ca,Ba͒SiO 4 :Eu 2+ ternary phosphors were screened in terms of photoluminescence ͑PL͒ intensity and color chromaticity at an excitation of 400 nm to determine their suitability for use in white-light-emitting diodes. As a result, several intermediate compounds ͑mixtures or solid solutions͒ were pinpointed in a specific composition range in the Li 2 ͑Sr,Ca,Ba͒SiO 4 :Eu 2+ ternary composition library. In particular, Li 2 ͑Ba 1−x Sr x ͒SiO 4 :Eu 2+ ͑0.3 Ͻ x Ͻ 0.6͒ showed the best performance in terms of both PL intensity and color chromaticity.Light-emitting diodes ͑LEDs͒ for solid-state lighting have significant potential in terms of energy savings and environmental advantages, and are expected to replace most gas discharge fluorescent lamps in the near future. 1,2 There are several ways of constituting white light based on the LED technique, each of which involves various phosphors which emit visible light by absorbing soft UV or blue light produced by LEDs. When LED phosphors are categorized with respect to their composition we can enumerate various oxides, sulfides ͑or chalcogenides͒, and nitrides ͑or oxynitrides͒. The representative oxide phosphors are Y 3 Al 5 O 12 :Ce 3+ and its variants, 3 and divalent europium-doped ortho-silicate phosphors. 4 These oxide phosphors emit yellow light and work best when combined with 460 nm blue-emitting LED chips, but all of them have a low color rendering index ͑CRI͒. A great deal of attention has been focused on sulfide ͑or chalcogenide͒ phosphors such as SrGa͑S,Se͒:Eu 2+ ͑green͒ and ͑Sr,Ca͒͑S,Se͒:Eu 2+ ͑red͒ due to their yellow-green and red color emission under soft UV excitations. However, the sulfide phosphors have a serious drawback with respect to long-term stability, though they exhibit high luminescent efficiency and improved CRI. In addition, nitride ͑or oxynitride͒ phosphors have been developed most recently and are still in the early stages of development. Nitride red phosphors such as divalent europium-doped CaAlSiN 3 and ͑Ca,Sr͒ 2 Si 5 N 8 are already commercially available, and Ca ͑or Li͒, ␣-sialon, 5,6 and strontium/barium nitridosilicates 7-9 are under consideration for use in white-LEDS ͑WLEDs͒. However, in-depth studies on the 5d energy in the above-described oxide and nitride phosphors are lacking, despite the successful commercialization of these phosphors.The aim of the present investigation is to examine some silicate phosphors such as Li 2 SrSiO 4 :Eu 2+ ͑LSSO͒, Li 2 CaSiO 4 :Eu 2+ ͑LCSO͒, and Li 2 BaSiO 4 :Eu 2+ ͑LBSO͒ phosphors based on their potential for use in WLEDs for LSSO, LCSO, and LBSO phosphors in association with their exact structure. In fact, LSSO, LCSO, and LBSO phosphors have...

We designed, synthesized, and characterized a series of three medium-bandgap conjugated polymers (PBDT­fDTBO, PBDT­fDTBT, and PBDT­fDTBS) consisting of fused dithienobenzo­chalcogenadiazole (fDTBX)-based weak electron-deficient and planar building blocks, which possess bandgaps of ∼2.01 eV. The fDTBX-based medium-bandgap polymers exhibit deep-lying HOMO levels (∼5.51 eV), which is beneficial for use in multijunction polymer solar cell applications. The resulting polymers with chalcogen atomic substitutions revealed that the difference in the electron negativity and atomic size of heavy atoms highly affects an intrinsic property, morphological feature, and photovoltaic property in polymer solar cells. The polymer solar cells based on sulfur-substituted medium-bandgap polymer showed power conversion efficiencies above 6% when blended with [6,6]-phenyl-C71-butyric acid methyl ester in a typical bulk-heterojunction single cell. These results suggest that the fDTBX-based medium-bandgap polymer is a promising alternative material for P3HT in tandem polymer solar cells for achieving high efficiency.

A multi‐objective genetic algorithm‐assisted combinatorial materials search (MOGACMS) strategy was employed to develop a new green phosphor for use in a cold cathode fluorescent lamp (CCFL) for a back light unit (BLU) in liquid crystal display (LCD) applications. MOGACMS is a method for the systematic control of experimental inconsistency, which is one of the most troublesome and difficult problems in high‐throughput combinatorial experiments. Experimental inconsistency is a very serious problem faced by all scientists in the field of combinatorial materials science. For this study, experimental inconsistency and material property were selected as dual objective functions that were simultaneously optimized. Specifically, in an attempt to search for promising phosphors with high reproducibility, luminance was maximized and experimental inconsistency was minimized using the MOGACMS strategy. A divalent manganese‐doped alkali alkaline germanium oxide system was screened using MOGACMS. As a result of MOGA reiteration, we identified a phosphor, Na2MgGeO4:Mn2+, with improved luminance and reliable reproducibility.

Two new hole-extraction materials, TPDI (5,10,15-triphenyl-5H-diindolo[3,2-a:3 0 ,2 0 -c]carbazole) and TBDI (5,10,15-tribenzyl-5H-diindolo[3,2-a:3 0 ,2 0 -c]carbazole), were synthesized and explored in planar heterojunction organic solar cells (OSCs). The synthesized materials have good transparency in the visible spectrum, high hole mobility, and compatible highest occupied molecular orbital (HOMO) values with the donor material, which make them excellent hole-extraction layers (HELs) for OSCs. The SubPc (subphthalocyanine chloride)/C 60 and SubNc (subnaphthalocyanine chloride)/C 60 OSCs with a TBDI HEL show impressive 35.9% and 29.1% improvements in power conversion efficiencies compared to reference devices. Their HOMO values were evaluated as 5.2-5.3 eV and hole mobilities were measured as 5.9-6.1 Â 10 À3 cm 2 V À1 s À1 at 0.3 MV cm À1 by the space-charge limited current method.

A genetic algorithm was employed in association with high-throughput synthesis and characterization in an attempt to search for red phosphors with high photoluminescent intensity. A tetravalent manganese-doped alkali earth germanium oxide system, with an emission color close to a desirable deep red, was screened with the assistance of a genetic algorithm to pinpoint the phosphor exhibiting the highest photoluminescence. As the genetic algorithm was in progress, the PL intensity increased and maximized in the fourth generation. The highest and the average PL intensity of the fourth generation improved by 23 and 120%, respectively, compared with that of the first generation.

No abstract