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A blue-luminescent Tm3+-activated ZnLaB5O10 material was initially synthesized via thermal solid-state reactions. Structural characterization and optical evaluations confirmed phase homogeneity and radiative characteristics of the crystalline products. Experimental data identified 3 mol% Tm3+ doping (x=0.03) as the critical concentration threshold before emission efficiency decline. Mechanistic studies revealed that multipolar electrical interactions dominate energy dissipation processes in over-doped systems. The optimized compound exhibited intense blue emission with CIE chromaticity values (0.1803, 0.1007), demonstrating suitability as a blueconversion material in w-LED architectures.

Fundamental numerical study on controlling chromaticity with the simplest diffractive structure is carried out. Observed various characteristics on transmission/reflection and dielectric/metal will be useful guidelines for practical optimisation of device structures.

Aromatic organic deep-blue emitters that exhibit thermally activated delayed fluorescence (TADF) can harvest all excitons in electrically generated singlets and triplets as light emission. However, blue TADF emitters generally have long exciton lifetimes, leading to severe efficiency decrease, i.e., rolloff, at high current density and luminance by exciton annihilations in organic light-emitting diodes (OLEDs). Here, we report a deep-blue TADF emitter employing simple molecular design, in which an activation energy as well as spin–orbit coupling between excited states with different spin multiplicities, were simultaneously controlled. An extremely fast exciton lifetime of 750 ns was realized in a donor–acceptor-type molecular structure without heavy metal elements. An OLED utilizing this TADF emitter displayed deep-blue electroluminescence (EL) with CIE chromaticity coordinates of (0.14, 0.18) and a high maximum EL quantum efficiency of 20.7%. Further, the high maximum efficiency were retained to be 20.2% and 17.4% even at high luminance. Deep-blue emitting organic materials with low exciton lifetime are required to realize efficient organic light-emitting diodes (OLEDs) at high brightness. Here, the authors report deep-blue OLEDs featuring thermally activated delayed fluorescence molecules with subnano-second exciton lifetime.

Phosphorescent organic light-emitting diodes (PHOLEDs) feature high efficiency 1 , 2 , brightness and colour tunability suitable for both display and lighting applications 3 . However, overcoming the short operational lifetime of blue PHOLEDs remains one of the most challenging high-value problems in the field of organic electronics. Their short lifetimes originate from the annihilation of high-energy, long-lived blue triplets that leads to molecular dissociation 4 – 7 . The Purcell effect, the enhancement of the radiative decay rate in a microcavity, can reduce the triplet density and, hence, the probability of destructive high-energy triplet–polaron annihilation (TPA) 5 , 6 and triplet–triplet annihilation (TTA) events 4 , 5 , 7 , 8 . Here we introduce the polariton-enhanced Purcell effect in blue PHOLEDs. We find that plasmon–exciton polaritons 9 (PEPs) substantially increase the strength of the Purcell effect and achieve an average Purcell factor (PF) of 2.4 ± 0.2 over a 50-nm-thick emission layer (EML) in a blue PHOLED. A 5.3-fold improvement in LT90 (the time for the PHOLED luminance to decay to 90% of its initial value) of a cyan-emitting Ir-complex device is achieved compared with its use in a conventional PHOLED. Shifting the chromaticity coordinates to (0.14, 0.14) and (0.15, 0.20) into the deep blue, the Purcell-enhanced devices achieve 10–14 times improvement over similarly deep-blue PHOLEDs, with one structure reaching the longest Ir-complex device lifetime of LT90 = 140 ± 20 h reported so far 10 – 21 . The polariton-enhanced Purcell effect and microcavity engineering provide new possibilities for extending deep-blue PHOLED lifetimes. Polariton-enhanced Purcell effects can be used to reduce the triplet density in blue phosphorescent organic light-emitting diodes, thereby extending their operational lifetimes by decreasing the annihilation of high-energy, long-lived blue triplets.

The Planckian locus—a shallow curved line in chromaticity space—delimits the range of common illuminant colours. When we allow mixtures of colours the locus becomes a convex set, sometimes called an illumination gamut. Convex sets are rather simple geometric objects and are often deployed in computer vision and colour imaging and their convexity is an essential property that makes certain calculations computationally feasible.In this paper, we consider a commonly used mapping applied to the colour coordinates of lights: the logarithmic operator. Specifically, we take the logarithm of the (R, G, B) camera responses. We argue that the physical definition of Planckian illumination and the physics of image formation imply that convexity should be preserved under this transformation.

This study assessed the relative effects of metameric (preserving illumination chromaticity) vs. chromatic illumination changes on the perceived quality of real fruits. 20 normal trichromats viewed four singly-presented fruits under three neutral metameric illuminations (differing in spectral power distribution with constant CCT of ∼6500K) and two broadband chromatic illuminations (∼2000K and ∼10000K) inside a white-walled lightroom illuminated by spectrally tuneable lamps. Participants’ ratings of nine fruit attributes were used to calculate Positive Attributes Scores (PAS) for each fruit-illumination pair. For two fruits (banana and pear), PAS varied significantly under metameric illumination changes, but not under chromatic illumination changes. PAS varied significantly under both metameric and chromatic illumination changes for orange, and under chromatic illumination changes only for red apple. The findings indicate that metameric illumination changes alter perceived food attributes via changes in fruit colour appearance, while changes in illumination chromaticity may influence perceived food quality independently of fruit colour appearance which is largely maintained via colour constancy.

Natural daylight varies continuously in chromaticity and illuminance over multiple timescales, shaped by solar geometry, atmospheric conditions, and surface reflections. To quantify these dynamics, we measured 4512 directional spectra, yielding 752 complete light field samples across four days at two locations under diverse weather conditions. Diffuse and directional components of daylight were separated, revealing a consistent tripartite daily pattern: rapid chromatic shifts at dawn and dusk, and relative stability around midday. Directional illumination exhibited larger and faster variations, particularly under clear skies, while diffuse illumination remained comparatively stable but less regular, likely due to surface reflections. Psychophysical measurements of temporal chromaticity discrimination thresholds [1] show asymmetries in perceptual sensitivity: shifts toward cooler CCTs (∼1.2 ΔE/s) are more easily detected than shifts toward warmer CCTs (∼2 ΔE/s), when starting from a cool daylight CCT (10,000 K). Natural rates of change at dawn and dusk (up to ∼0.4 ΔE/s) are generally well below these perceptual thresholds, with only directional components under clear skies transiently approaching threshold visibility. These asymmetries may reflect functional dissociations between perceptual stability and circadian regulation, with non-visual pathways remaining sensitive to structured daylight changes even when conscious perception is suppressed.

Intrinsic polymer room-temperature phosphorescence (IPRTP) materials have attracted considerable attention for application in flexible electronics, information encryption, lighting displays, and other fields due to their excellent processabilities and luminescence properties. However, achieving multicolor long-lived luminescence, particularly white afterglow, in undoped polymers is challenging. Herein, we propose a strategy of covalently coupling different conjugated chromophores with poly(acrylic acid (AA)-AA-N-succinimide ester) (PAA-NHS) by a simple and rapid one-pot reaction to obtain pure polymers with long-lived RTPs of various colors. Among these polymers, the highest phosphorescence quantum yield of PAPHE reaches 14.7%. Furthermore, the afterglow colors of polymers can be modulated from blue to red by introducing three chromophores into them. Importantly, the acquired polymer TPAP-514 exhibits a white afterglow at room temperature with the chromaticity coordinates (0.33, 0.33) when the ratio of chromophores reaches a suitable value owing to the three-primary-color mechanism. Systematic studies prove that the emission comes from the superposition of different triplet excited states of the three components. Moreover, the potential applications of the obtained polymers in light-emitting diodes and dynamic anti-counterfeiting are explored. The proposed strategy provides a new idea for constructing intrinsic polymers with diverse white-light emission RTPs. It is challenging to achieve multicolor long-lived room temperature phosphorescence in intrinsic polymers, especially for white afterglow. Here, the authors report a strategy to obtain pure white afterglow micro-crosslinked polymers by covalently coupling different conjugated chromophores with precursors through a simple and rapid one-pot reaction.

NaBiF4 nanocrystalline particles were synthesized by means of a facile precipitation synthesis route to explore upconversion emission properties when doped with lanthanide ions. In particular, the incorporation of the Yb3+-Ho3+-Ce3+ triad with controlled ion concentration facilitates near-IR pumping conversion into visible light, with the possibility of color emission tuning depending on Ce3+ doping amount. We observed that introducing a Ce3+ content up to 20 at.% in NaBiF4:Yb3+/Ho3+, the chromaticity progressively turns from green for the Ce3+ undoped system to red. This is due to cross-relaxation mechanisms between Ho3+ and Ce3+ ions that influence the relative efficiency of the overall upconversion pathways, as discussed on the basis of a theoretical rate equation model. Furthermore, experimental results suggest that the photoexcitation of intra-4f Ho3+ transitions with light near the UV-visible edge can promote downconverted Yb3+ near-IR emission through quantum cutting triggered by Ho3+-Yb3+ energy transfer mechanisms. The present study evidences the potentiality of the developed NaBiF4 particles for applications that exploit lanthanide-based light frequency conversion and multicolor emission tuning.

Semitransparent organic photovoltaic cells (ST-OPVs) are emerging as a solution for solar energy harvesting on building facades, rooftops, and windows. However, the trade-off between powerconversion efficiency (PCE) and the average photopic transmission (APT) in color-neutral devices limits their utility as attractive, power-generating windows. A color-neutral ST-OPV is demonstrated by using a transparent indium tin oxide (ITO) anode along with a narrow energy gap nonfullerene acceptor near-infrared (NIR) absorbing cell and outcoupling (OC) coatings on the exit surface. The device exhibits PCE = 8.1 ± 0.3% and APT = 43.3 ± 1.2% that combine to achieve a light-utilization efficiency of LUE = 3.5 ± 0.1%. Commission Internationale d’eclairage chromaticity coordinates of (0.38, 0.39), a color-rendering index of 86, and a correlated color temperature of 4,143 K are obtained for simulated AM1.5 illumination transmitted through the cell. Using an ultrathin metal anode in place of ITO, we demonstrate a slightly green-tinted STOPV with PCE = 10.8 ± 0.5% and APT = 45.7 ± 2.1% yielding LUE = 5.0 ± 0.3% These results indicate that ST-OPVs can combine both efficiency and color neutrality in a single device.