High Correlated Color Temperature Research Articles

Photoluminescence investigation of novel reddish-orange phosphor Li2NaBP2O8:Sm3+ with high CP and low CCT

The exploration of appropriate inorganic phosphors with high color purity (CP) and low correlated color temperature (CCT) has always been a hot issue for solid state light applications. In this work, we have developed series of Sm3+ doped Li2NaBP2O8 (abbreviated as: LNBP) phosphors by means of the solid state synthesis route. The crystalline phase compositions, micromorphology, valence state of elements as well as photoluminescence properties were systematically illustrated. Upon the excitation wavelength at 400 nm, emission peaks are located at 561，597，643 and 699 nm, corresponding to the 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions of Sm3+ in the same order. The optimal doping amount of Sm3+ ions is 2 mol% for the reddish-orange photoluminescence of the LNBP:Sm3+ phosphor system. The critical energy transfer distance, mechanism of concentration quenching, CIE chromaticity coordinate, CP, CCT and internal quantum efficiency were extensively investigated. The title product might be considered as a promising candidate of phosphor in near UV-based warm white LEDs.

Non-image forming effects of illuminance and correlated color temperature of office light on alertness, mood, and performance across cognitive domains

Research has explored acute effects of light level and correlated color temperature (CCT) of indoor lighting on subjective measures of alertness and task performance during daytime. Yet, these investigations did not render a conclusive or consistent finding on the relative contribution of illuminance and CCT on various cognitive domains. The current study (N = 57) investigated diurnal effects of illuminance level (100 lx vs. 1000 lx at eye level) and correlated color temperature (3000 K vs. 6500 K) in a simulated office environment on subjective alertness and performance in sustained attention, response inhibition, conflict monitoring, and working memory. Moreover, effects on mood and appraisals were explored. The findings revealed that the high vs. low CCT manipulation elicited no statistically significant benefits on subjective alertness and task performance, but revealed an increase in negative affect. Exposure to high vs. low illuminance rendered subtle benefits on participants’ mood and selectively improved performance. Reaction speed in the Go/No-go task and Flanker task (only incongruent trials) were significantly enhanced with 1000 lx compared to 100 lx lighting, but not statistically significant in the PVT task or the PVSAT task. Effects are discussed in consideration of task type and melanopic activation under the various light conditions.

The effect of illuminance and correlated colour temperature on perceived comfort according to reading behaviour in a capsule hotel

We investigated the effect of illuminance and correlated colour temperature (CCT) on the subjective evaluation of users' reading behaviour in a narrow space (i.e. a capsule hotel). Participants (N = 18; 15 men, 3 women; mean age = 21.9 years, SD = 0.4 years; age range = 21–23 years) were Japanese university students and graduate students. Experiments were conducted within four behavioural conditions that differed in six distinct illuminance (i.e. 150 lx and 300 lx) and CCT (i.e. 2800 K, 5000 K, and 6700 K) combinations. Because of the subjective evaluation of the space using the 7-level semantic differential method, participants did not experience pressure in the experimental space when it satisfied illumination standards. Sense of security was significantly influenced by CCT rather than illumination. Higher CCT was associated with higher spatial brightness. Lower CCT was associated with a higher sense of security, restfulness, and positive feelings. Brightness, sense of security, restfulness, feelings of fatigue, and concentration were all significantly impacted by the behavioural conditions. These findings suggest that providing a user-friendly and user-controlled lighting system will likely increase the satisfaction individuals experience when staying in a capsule room.

Rsp ratio approach for evaluation of scotopic/photopic ratios of light source performance at varying CCTs.

Scotopic/photopic ratio (S/P ratio, or Rsp) is an absolute measure of a light source's performance under the mesopic vision state. However, there is more potential for a light source to reach higher mesopic performance at higher correlated color temperatures (CCTs), and these cannot be evaluated. We proposed an Rsp ratio metric to examine relative performance of the S/P ratio at a corresponding CCT. Based on examination of a large set of light sources, we established the Rsp-CCT and Rsp ratio-CCT relations of different light source types. On investigating previously reported high S/P ratio light sources with the proposed metric, it shows high effectiveness in evaluating relative mesopic performance when considering CCT issues.

Enhancement of angular color uniformity of remote-phosphor-converted light-emitting diodes by electrospun-nanofiber diffusing films

We propose electrospun-nanofiber diffusing films to enhance the angular color uniformity (ACU) of remote-phosphor-converted light-emitting diodes (RPC-LEDs). Poly(vinylidene fluoride) electrospun nanofibers/acrylic composite films with different nanofiber thicknesses are investigated. An optimal composite film is obtained based on the balance between the ACU enhancement and luminous flux reduction, which can be applied to RPC-LEDs with different correlated color temperatures (CCTs) to enhance the ACU with a small luminous-flux loss, particularly at higher CCTs. Therefore, the composite films can effectively enhance the ACU of RPC-LEDs while maintaining a high luminous flux.

Workplace lighting for improving alertness and mood in daytime workers.

Exposure to light plays a crucial role in biological processes, influencing mood and alertness. Daytime workers may be exposed to insufficient or inappropriate light during daytime, leading to mood disturbances and decreases in levels of alertness. To assess the effectiveness and safety of lighting interventions to improve alertness and mood in daytime workers. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, seven other databases; ClinicalTrials.gov and the World Health Organization trials portal up to January 2018. We included randomised controlled trials (RCTs), and non-randomised controlled before-after trials (CBAs) that employed a cross-over or parallel-group design, focusing on any type of lighting interventions applied for daytime workers. Two review authors independently screened references in two stages, extracted outcome data and assessed risk of bias. We used standardised mean differences (SMDs) and 95% confidence intervals (CI) to pool data from different questionnaires and scales assessing the same outcome across different studies. We combined clinically homogeneous studies in a meta-analysis. We used the GRADE system to rate quality of evidence. The search yielded 2844 references. After screening titles and abstracts, we considered 34 full text articles for inclusion. We scrutinised reports against the eligibility criteria, resulting in the inclusion of five studies (three RCTs and two CBAs) with 282 participants altogether. These studies evaluated four types of comparisons: cool-white light, technically known as high correlated colour temperature (CCT) light versus standard illumination; different proportions of indirect and direct light; individually applied blue-enriched light versus no treatment; and individually applied morning bright light versus afternoon bright light for subsyndromal seasonal affective disorder.We found no studies comparing one level of illuminance versus another.We found two CBA studies (163 participants) comparing high CCT light with standard illumination. By pooling their results via meta-analysis we found that high CCT light may improve alertness (SMD -0.69, 95% CI -1.28 to -0.10; Columbia Jet Lag Scale and the Karolinska Sleepiness Scale) when compared to standard illumination. In one of the two CBA studies with 94 participants there was no difference in positive mood (mean difference (MD) 2.08, 95% CI -0.1 to 4.26) or negative mood (MD -0.45, 95% CI -1.84 to 0.94) assessed using the Positive and Negative Affect Schedule (PANAS) scale. High CCT light may have fewer adverse events than standard lighting (one CBA; 94 participants). Both studies were sponsored by the industry. We graded the quality of evidence as very low.We found no studies comparing light of a particular illuminance and light spectrum or CCT versus another combination of illuminance and light spectrum or CCT.We found no studies comparing daylight versus artificial light.We found one RCT (64 participants) comparing the effects of different proportions of direct and indirect light: 100% direct lighting, 70% direct lighting plus 30% indirect lighting, 30% direct lighting plus 70% indirect lighting and 100% indirect lighting. There was no substantial difference in mood, as assessed by the Beck Depression Inventory, or in adverse events, such as ocular, reading or concentration problems, in the short or medium term. We graded the quality of evidence as low.We found two RCTs comparing individually administered light versus no treatment. According to one RCT with 25 participants, blue-enriched light individually applied for 30 minutes a day may enhance alertness (MD -3.30, 95% CI -6.28 to -0.32; Epworth Sleepiness Scale) and may improve mood (MD -4.8, 95% CI -9.46 to -0.14; Beck Depression Inventory). We graded the quality of evidence as very low. One RCT with 30 participants compared individually applied morning bright light versus afternoon bright light for subsyndromal seasonal affective disorder. There was no substantial difference in alertness levels (MD 7.00, 95% CI -10.18 to 24.18), seasonal affective disorder symptoms (RR 1.60, 95% CI 0.81, 3.20; number of participants presenting with a decrease of at least 50% in SIGH-SAD scores) or frequency of adverse events (RR 0.53, 95% CI 0.26 to 1.07). Among all participants, 57% had a reduction of at least 50% in their SIGH-SAD score. We graded the quality of evidence as low.Publication bias could not be assessed for any of these comparisons. There is very low-quality evidence based on two CBA studies that high CCT light may improve alertness, but not mood, in daytime workers. There is very low-quality evidence based on one CBA study that high CCT light may also cause less irritability, eye discomfort and headache than standard illumination. There is low-quality evidence based on one RCT that different proportions of direct and indirect light in the workplace do not affect alertness or mood. There is very low-quality evidence based on one RCT that individually applied blue-enriched light improves both alertness and mood. There is low-quality evidence based on one RCT that individually administered bright light during the afternoon is as effective as morning exposure for improving alertness and mood in subsyndromal seasonal affective disorder.

White emission enhancement of Ca5(PO4)3Cl:Dy3+ phosphor with Li+/Eu3+ co-doping for white light-emitting diodes

Dysprosium doped chlorapatite, Ca5(PO4)3Cl:Dy3+ white-emitting phosphors were synthesized by a solid-state reaction method. The effects of synthesis temperature, Dy3+ doping concentration, Eu3+ co-doping concentration and charge compensator Li+ co-doping on the crystal structures and luminescence properties of Ca5(PO4)3Cl:Dy3+ samples were investigated. Ca5(PO4)3Cl:Dy3+, Eu3+ and Ca5(PO4)3Cl:Dy3+, Li+ phosphors with standard Ca5(PO4)3Cl structure were prepared by heating above 900 °C, and the doped Dy3+, Eu3+/Li+ ions had no effect on the crystal structure. Under ultraviolet excitation at 366 nm, the emission spectra of Ca5(PO4)3Cl:Dy3+ phosphors exhibited two characteristic peaks of Dy3+ at 484 and 577 nm, which corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 electron transitions, respectively. Both blue and yellow emissions within a single-component host would constitute the white light. The white emission intensity of Ca5(PO4)3Cl:Dy3+ was enhanced markedly by Li+ co-doping as charge compensator. Moreover, Eu3+ co-doped Ca5(PO4)3Cl:Dy3+ phosphor showed an excellent warm white light with high chromaticity coordinates and low correlated color temperature though an additional red emission of Eu3+. The results indicate that these Ca5(PO4)3Cl:Dy3+, Eu3+/Li+ phosphors have potential applications in the field of white light-emitting diodes as single-component white-emitting phosphors.

Does the iPad Night Shift mode reduce melatonin suppression?

The increased use of self-luminous displays, especially in the evening prior to bedtime, has been associated with melatonin suppression, delayed sleep and sleep curtailment. The present study set out to investigate whether the Night Shift application provided by Apple Inc. for use on its portable electronic devices is effective for reducing acute melatonin suppression, a well-established marker of circadian phase. Participants experienced four experimental conditions: a dim light control, a high circadian stimulus true positive intervention and two Night Shift interventions delivering low and high correlated colour temperature light from the devices. Melatonin suppression did not significantly differ between the two Night Shift interventions, which indicates that changing the spectral composition of self-luminous displays without changing their brightness settings may be insufficient for preventing impacts on melatonin suppression.

The impact of fluorescent and led lighting on students attitudes and behavior in the classroom

Introduction: This study examined empirical research on the effects of high correlated color temperature light-emitting diodes (LED) and fluorescent lighting on students in the classroom. LED is becoming the most recent lighting option for optimal energy efficiency over fluorescent technology. Background: A review of the literature indicates correlated color temperature (CCT) of lighting has non-visual effects on students, with higher CCT positively impacting attitudes and behavior. The review also revealed current studies regarding dynamic or tunable lighting that adjusts CCT based on desired activity and mood. Data from an original survey analyzed teacher insights and perceptions regarding student attitudes and behaviors associated with existing classroom lighting and the impact of higher color temperature LED. Methods: Participants were pre-K through high school qualified teachers from three schools and/or personal contacts of the principal investigator. Seventy-five teachers responded to the online questionnaire. The survey data suggests teachers perceive higher color temperature lighting positively impacts student alertness, attitude, and energy level; and adjusting light levels throughout a school day positively impacts student engagement. Results and conclusion: Results supported the perception of higher correlated color temperature lighting positively impacting alertness, attitude, and energy level. Findings also supported the ability to change light levels throughout the school day to positively impact student engagement and mood. There were mixed results regarding higher correlated color temperature impacting attention and on-task/off- task behaviors. Results regarding the impact of sound and flickering from fluorescent lights were not significant.

Discovery of novel solid solution Ca3Si3\u2212xO3+xN4\u22122x: Eu2+ phosphors: structural evolution and photoluminescence tuning

Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca3Si3−xO3+xN4−2x: Eu2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca3Si3−xO3+xN4−2x: Eu2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.

(Invited) Narrow Band Emission of Nitrides Phosphors and All Inorganic Perovskite Quantum Dots for the Application in Light Emitting Diodes

A narrow band emission nitride SrLiAl3N4:Eu2+ (SLA) red phosphor prepared through a high-pressure solid state reaction was coated with organosilica layers in 400 ~ 600 nm thickness to improve its waterproof property. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70% of its initial EQE after being aged for 5 days in harsh conditions. White light-emitting diodes (LEDs) of SLA red-phosphors and commercial Y3Al5O12:Ce3+ (YAG:Ce) yellow-phosphor on a blue-InGaN chip were shown high color rendition (CRI = 89, R9 = 69) and low correlated color temperature of 2406 K. All-inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (PQDs) with narrow emission bad were synthesized by hot injection methods. We propose an efficient and simple method to prevent the anion-exchange effect. We mixed green CsPbBr3 PQDs with purchased mesoporous silica. We applied the new PQD-based LEDs for backlight displays. Our white LED device for backlight display passed through a color filter with an NTSC value of 113% and Rec. 2020 of 85%. For lighting application, we used red perovskite quantum dots assisted by a yellow YAG:Ce phosphor were integrated on a blue chip. This warm white light with CCT (3328K), high color rendering index (CRI = 84.7) and a super high value of saturated red color component R9 as 96. Nitrides phosphors and all inorganic quantum dots were a good candidate for the application of white light LEDs with narrow emission band.

Optical enhancement of phosphor-converted wLEDs using glass beads

YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite.

A promising orange-yellow-emitting phosphor for high power warm-light white LEDs: Pure-phase synthesis and photoluminescence properties

The high correlated colour temperature (CCT) and deficient thermal stability of widely-used YAG:Ce and InGaN white light systems prompt an urgent need for more outstanding succedaneum phosphors, among which Ce-doped La3Si6N11 (LSN:Ce) phosphor has the best performance in the yellow-orange area. However, it still has not gained popularity due to its low quantum efficiency and luminance quality, caused by many factors such as irregular particle morphology and impure chemical composition, especially the difficulty of obtaining a single phase without LaSi3N5 impurity. By doping with different alkaline-earth metal elements and adjustment of the lanthanum/silicon ratio in the raw materials, LSN:Ce and MLSN:Ce (M = Ca, Ba and Sr) phosphors with high purity were synthesised in this work. Compared to Ca and Sr, doping with Ba produced a better result, not only in the crystallisation of the LSN phase, but also in the red shift of the phosphor emission. To further improve the purity of LSN phosphors, the Si/La molar ratio was increased from 2:1 to 1:1.5, and finally resulting in a single phase when the ratio reached 1:1. The white LEDs fabricated with the LSN:Ce & BaLSN:Ce phosphors and InGaN blue light chips had lower CCTs at 3900 K and 3300 K, indicating the great potential of the phosphor for application in high power and display lighting.

Facile fabrication of Eu3+ activated YAG:Ce3+ glass ceramics exhibiting high thermal stability and tunable luminescence for warm white LEDs

To relieve the issues of high correlated color temperature and low color rendering index, it is urgent to develop an inorganic color converter materials with both red- and yellow-emission to replace the conventional organic resin/silicon-based color converter and acquire warm white light-emitting diodes (WLEDs). In our work, transparent glass–ceramics (GCs) containing Ce3+:Y3Al5O12 (Ce3+:YAG) yellow phosphors and Eu3+ ions are successfully fabricated by using low temperature co-sintering technique. And then the microstructure and luminescence properties of the GC are investigated in detail. Importantly, the impact of Ce3+:YAG phosphors concentration, Eu3+ ions concentration, co-sintering time and the GC thickness on optical performances are also systematically demonstrated. Impressively, the as-fabricated samples exhibit an efficient red emission at 611 nm owing to the 5D0→7F2 transition of Eu3+. Subsequently, the temperature-dependent luminescence and thermal quenching is also investigated. Finally, the constructed WLEDs show an optimal luminous efficacy of 120.85 lm/W, a color rendering index of 70.2 and a correlated color temperature of 5267 K. All the results indicate that the as-fabricated GC would have potential practical applications in high-power WLEDs.

Energy transfer properties and enhanced color rendering index of chromaticity tunable green-yellow-red-emitting Y_3Al_5O_12: Ce^3+, Cr^3+ phosphors for white light-emitting diodes

White light-emitting diodes using YAG: Ce3+ phosphors suffer from the deficiency of red component, leading to a low color rendering index (CRI) and a high correlated color temperature (CCT). Herein, a yellow-red single-phase YAG: Ce3+, Cr3+ phosphor was synthesized by a traditional solid-state reaction. Compared with Cr3+ ion single-doped YAG phosphor, the emission intensity in the far-red region of the co-doped YAG: Ce3+, Cr3+ sample increases because of the energy transfer from Ce3+ ions to Cr3+ ions. For sample Y3Al5O12: 0.02Ce3+, 0.008Cr3+ phosphor, the internal and external quantum efficiencies are 58.9% and 46.7%, respectively. And, the fabricated white LED shows a CCT of 6085 K at CIE 1931 coordinate (0.3208, 0.3273). Moreover, the CRI is as high as 77.9 while that of the corresponding Ce3+ single-doped YAG phosphor is only 63.2. Thus, the Ce3+ and Cr3+ co-doped YAG phosphors are suitable for white light-emitting diodes (WLEDs).

The effect of correlated colour temperature of lighting on thermal sensation and thermal comfort in a simulated indoor workplace

The ‘hue-heat’ hypothesis states that an environment which has wavelengths predominantly toward the red end of the visual spectrum feels ‘warm’ and one with wavelengths mainly toward the blue end feels ‘cool’. In order to test the hypothesis and to study the impacts of the correlated colour temperature of a light source on thermal sensation and thermal comfort, a study was conducted in a test room illuminated with an Light Emitting Diode (LED) lighting system with an adjustable correlated colour temperature where air temperature, air velocity, and relative humidity were kept constant. The correlated colour temperature of lighting inside the test room was changed gradually while keeping the colour rendering index values greater than 90, an illuminance level of 500 lx, and chromaticity difference (Duv) values within the limits of ±0.005. Sixteen study subjects were exposed to a ‘high room temperature’ (25℃) and a ‘low room temperature’ (20℃) on different days. The subjects were adapted to low correlated colour temperature (2700 K), medium correlated colour temperature (4000 K), and high correlated colour temperature (6200 K) lighting for 10 min and subsequently completed the questionnaire about their thermal comfort and thermal sensation. The results of this survey did not provide support for the hue-heat hypothesis and indicated that people felt thermally more comfortable in an indoor workplace at the correlated colour temperature of 4000 K than at the correlated colour temperature of 2700 K or 6200 K.

ChemInform Abstract: A Review on Mn4+ Activators in Solids for Warm White Light‐Emitting Diodes

AbstractReview: 80 refs.

Effect of the Phosphor Permanent Substrate on the Angular CCT for White Thin-Film Flip-Chip Light-Emitting Diodes

This paper developed a phosphor layer applied for thin-film flip-chip light-emitting diodes (TFFC-LEDs) to produce uniform phosphor-converted TFFC white LEDs (TFFC-WLEDs) by combination of laser liftoff, secondary transferring, and surface roughening process. The spin-coating method was used for phosphor layer fabrication onto a substrate to form the phosphor permanent substrate. The TFFC-LEDs were then bonded onto the permanent substrate. From the results, the blue TFFC GaN-based LED with roughened u-GaN surface on a glass substrate (TFRG-LED) demonstrated a 54.2% (at 350 mA) enhancement in light output power, compared with a blue flip-chip GaN-on-sapphire based LED. As the TFFC GaN/phosphor-/glass-based white LED with roughened u-GaN surface (TFRG-WLED) was operated at a forward-bias current of 350 mA, the enhancement of luminous flux was increased by 75.5%, compared with a TFFC GaN/phosphor template-/glass-based white LED. The angular correlated color temperature (CCT) deviation of a TFRG-WLED can be reduced to 1279 K in the range from −75° to +75° at 5000–6000 K application. The TFRG-WLED was fabricated on the glass substrate with the roughened u-GaN surface and the structure of phosphor layer closed to the u-GaN. These kinds of FRGB-WLED structure contribute to a better light extraction characteristic and a higher CCT stability.

Effect of color temperature on melatonin production for illumination of working environments

We studied the influence of correlated color temperature (CCT) of 7 polychromatic white light illuminations (1600 K–14,000 K, 200 lx) in two experiments.Visual performance was tested in 17 students (8 men) during daytime. Visual acuity, contrast sensitivity and sleepiness did not vary with illuminations but polychromatic white light of <2000 K impaired color discrimination.Melatonin synthesis was tested with weekly intervals in 8 trials from 10pm to 2am (7 polychromatic illuminations and a dim light reference (<0.1 lx)) in 16 students (9 men, semi-recumbent position). Melatonin suppression was almost negligible for CCT <2000 K but increased with increasing CCT. ConclusionsCCTs <2000 K are not suitable for work places. Polychromatic white light with higher CCTs and significant melatonin suppression is expected to shift the circadian rhythm and to accelerate the adaptation to night work. This effect should be enhanced with elevation of luminance.

A thermally stable warm WLED obtained by screen-printing a red phosphor layer on the LuAG:Ce3+ PiG substrate

Currently, phosphor-in-glass (PiG) approach draws great attention because of its excellent thermal resistance and facile process in WLED fabrication. However, the red light deficiency results in high correlated color temperature (CCT) and low color rendering index (CRI) in white light-emitting diode (WLED). Herein, a new LuAG:Ce3+ phosphor-in-glass (Lu-PiG) combining with the CaAlSiN3:Eu2+ red phosphor layer was synthesized by the low temperature co-sintering and screen-printing techniques, which was experimentally demonstrated to replace the conventional polymer-based phosphor converter and realized the chromaticity tuning for LuAG:Ce3+ phosphor with WLED. The Lu-PiG constructed WLED exhibited excellent thermal stability, but it still showed a typical cold white light resulting from the absence of red light component. Therefore, a stacking geometric configuration by screen-printing a red phosphor layer on the Lu-PiG substrate (R&Lu-PiG) was designed to solve red deficiency problem. The R&Lu-PiG color converter showed an excellent thermal stability with only 8.2% emission loss compared to the Lu-PiG when elevating temperature from 303K to 433K. By adjusting the CaAlSiN3:Eu2+ phosphor content in the layer, we obtained a high-performance warm WLED with a luminous efficacy of 102.1lm/W, a CCT of 3410K and a CRI of 76.5 under 20mA current driving. Thus, it is expected that this developed R&Lu-PiG color converters could have large potential applications in high-power warm WLED.