Abstract
Designing new single‐phase white phosphors for solid‐state lighting is a challenging trial–error process as it requires to navigate in a multidimensional space (composition of the host matrix/dopants, experimental conditions, etc.). Thus, no single‐phase white phosphor has ever been reported to exhibit both a high color rendering index (CRI ‐ degree to which objects appear natural under the white illumination) and a tunable correlated color temperature (CCT). In this article, a novel strategy consisting in iterating syntheses, characterizations, and machine learning (ML) models to design such white phosphors is demonstrated. With the guidance of ML models, a series of luminescent hybrid lead halides with ultra‐high color rendering (above 92) mimicking the light of the sunrise/sunset (CCT = 3200 K), morning/afternoon (CCT = 4200 K), midday (CCT = 5500 K), full sun (CCT = 6500K), as well as an overcast sky (CCT = 7000 K) are precisely designed.
Highlights
In lighting and display industries, phosphor converted white light-emitting diodes have been widely adopted owing to their high luminous flux, high efficacy and long lifespan.[1,2] Current pcwLEDs devices consist in a blue chip coated with yellow and red phosphors or an ultraviolet (UV) chip with red, green and blue phosphors.[3]
A methodology to precisely design white emitters with ultra-high CRI and tunable Correlated Color Temperature (CCT) is essential for the concept UV chip + single-phase white phosphor to be used in future pc-wLED technology
Such hybrid metal halides can exhibit two emissions originating from the recombination of free excitons (FE) and the recombination of self-trapped excitons (STE). [11,19] No photoemission from the organic molecule is expected in (TDMP)PbX4 as the isostructural (TDMP)SnX4 compounds showed only a very weak photoemission originating from the recombination of free excitons
Summary
In lighting and display industries, phosphor converted white light-emitting diodes (pc-wLEDs) have been widely adopted owing to their high luminous flux, high efficacy and long lifespan.[1,2] Current pcwLEDs devices consist in a blue chip coated with yellow and red phosphors or an ultraviolet (UV) chip with red, green and blue phosphors.[3] The combination of emissions originating from the chip and the mixture of different phosphors provides an illumination over the entire visible spectrum.[4] issues such as the reabsorption of emissions, the heterogeneous particle sizes, and the non-uniformity of the luminescence properties from different phosphors make the white emission difficult to control and to be stabilized over time.[5,6,7] As a result, low CRI (typically below 80) is the main limitation of the commercialized wLEDs.[8,9,10] In this context, the strategy of combining UV chips and a single-phase white phosphor exhibiting multiple emission bands has recently drawn new attention To design such phosphors, the intensity / wavelength of the emissions must be tuned.
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