Structural Optimization of BODIPY Derivatives: Achieving Stable and Long-Lived Green Emission in Hyperfluorescent OLEDs.

Boron dipyrromethene (BODIPY) derivatives are widely studied as terminal emitters in organic light-emitting diodes (OLED) due to their narrow emission and high photoluminescence quantum yield (PLQY). However, the strategy for precisely tuning their emission toward a high color purity is still challenging. Herein, we developed a new design strategy to regulate the emission of BODIPY derivatives by modifying the electronic and steric dominance using functionalities, such as nitrile, pentafluorophenyl, diethyl, and monobenzyl. These rational modifications yielded a series of four novel green BODIPY emitters, namely, tPN-BODIPY, tPPP-BODIPY, tPBn-BODIPY, and tPEN-BODIPY, each benefited with a tuned emissions range of 517 to 542 nm with a narrow fwhm of 25 nm and high photoluminescence quantum yield up to 96%. Among these synthesized BODIPYs, an unsymmetrical tPBn-BODIPY was chosen as a final dopant (FD) to explore its application in OLED devices. The fabricated TADF sensitized fluorescence-OLED (TSF-OLED) exhibits a narrow band pure green emission at 531 nm with corresponding CIE coordinates of (x, y) = (0.27, 0.68) and a maximum external quantum efficiency (EQE) of 20%. Furthermore, the TSF-OLED displayed an exceptionally prolonged device operational lifetime (LT90) of 210 h at an initial luminescence of 3000 cd m-2.

Forthcoming hyperfluorescence display technology: relevant factors to achieve high-performance stable organic light emitting diodes.

Over the decade, there have been developments in purely organic thermally activated delayed fluorescent (TADF) materials for organic light-emitting diodes (OLEDs). However, achieving narrow full width at half maximum (FWHM) and high external quantum efficiency (EQE) is crucial for real display industries. To overcome these hurdles, hyperfluorescence (HF) technology was proposed for next-generation OLEDs. In this technology, the TADF material was considered a sensitizing host, the so-called TADF sensitized host (TSH), for use of triplet excitons via the reverse intersystem crossing (RISC) pathway. Since most of the TADF materials show bipolar characteristics, electrically generated singlet and triplet exciton energies can be transported to the final fluorescent emitter (FE) through Förster resonance energy transfer (FRET) rather than Dexter energy transfer (DET). This mechanism is possible from the S1 state of the TSH to the S1 state of the final fluorescent dopant (FD) as a long-range energy transfer. Considering this, some reports are available based on hyperfluorescence OLEDs, but the detailed analysis for highly efficient and stable devices for commercialization was unclear. So herein, we reviewed the relevant factors based on recent advancements to build a highly efficient and stable hyperfluorescence system. The factors include an energy transfer mechanism based on spectral overlapping, TSH requirements, electroluminescence study based on exciplex and polarity system, shielding effect, DET suppression, and FD orientation. Furthermore, the outlook and future positives with new directions were discussed to build high-performance OLEDs.

Leukemia in infants.

OBJECTIVE: Acute Leukemia is rare in infants. It is characterized by non-specific symptomatology requiring a high index of suspicion on the part of a pediatrician for referral and diagnosis. It has peculiar biological features, unresponsiveness to treatment and poor prognosis. METHODS: Eighteen infants with acute leukemia were seen during 1994 to 2001 and were analyzed on the basis of clinical and laboratory data. There were 13 cases of Acute Lymphoblastic Leukemia (ALL), 4 cases of Acute Myeloid Leukemia (AML) and one case remained unclassifiable, as the surface markers could not be done. Morphologically 9/13 cases of ALL were of FAB L1 type and remaining of L2 subtype, and 2/4 cases of AML were of FAB M1 type and remaining of M2 subtype. RESULT: Clinical data was available completely only in 11 cases. Hyperleucocytosis was present in 4 cases, organomegaly in 8 cases and lympadenopathy in 5 cases. One patient presented with a chloroma in the retrorbital region although there was no parenchymal involvement of the brain. Immunophenotyping could be done in 13 cases, where 7 cases were diagnosed as CALLA positive-ALL (HLADR+, CD19+, CD10+), 2 cases as Early Pre-B ALL (HLADR+, CD19+, CD10 negative), one as T ALL (cCD3+, CD2+, CD7+) and 3 cases as AML (CD13+, CD33+, HLADR+). None of our patients received treatment.