Colour tuning in white hybrid inorganic/organic light-emitting diodes
Journal of Physics D: Applied Physics
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Bruckbauer, J., Brasser, C., Findlay, N., Edwards, P., Wallis, D., Skabara, P., & Martin, R. (2016). Colour tuning in white hybrid inorganic/organic light-emitting diodes. Journal of Physics D: Applied Physics, 49 (40. 405103)https://doi.org/10.1088/0022-3727/49/40/405103
White hybrid inorganic/organic light-emitting diodes (LEDs) were fabricated by combining a novel organic colour converter with a blue inorganic LED. An organic small molecule was specifically synthesised to act as down-converter. The characteristics of the white colour were controlled by changing the concentration of the organic molecule based on the BODIPY unit, which was embedded in a transparent matrix, and volume of the molecule and encapsulant mixture. The concentration has a critical effect on the conversion efficiency, i.e. how much of the absorbed blue light is converted into yellow light. With increasing concentration the conversion efficiency decreases. This quenching effect is due to aggregation of the organic molecule at higher concentrations. Increasing the deposited amount of the converter does not increase the yellow emission despite more blue light being absorbed. Degradation of the organic converter was also observed during a period of 15 months from LED fabrication. Angular-dependent measurements revealed slight deviation from a Lambertian profile for the blue and yellow emission peaks leading to a small change in ‘whiteness’ with emission angle. Warm white and cool white light with correlated colour temperatures of 2770K and 7680K, respectively, were achieved using different concentrations of the converter molecule. Although further work is needed to improve the lifetime and poor colour rendering, these hybrid LEDs show promising results as an alternative approach for generating white LEDs compared with phosphor-based white LEDs.
white hybrid LEDs, organic colour converter, energy down-converter, BODIPY, colorimetry
Is supplemented by: https://doi.org/10.15129/3bd82700-5914-48fa-8015-ac90d5ff3071
The authors would like to thank UK EPSRC (Grant Nos. EP/ I012591/1 ‘Lighting the Future’ and EP/L016982/1 ‘Next generation white LEDs using hybrid inorganic/organic semiconductor nanostructures for general illumination and wireless communication’) for financial support. DJW received funding through EPSRC’s Manufacturing Fellowship in Gallium Nitride (EP/ N01202X/1). Additionally, PJS thanks the Royal Society for a Wolfson Research Merit Award.
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External DOI: https://doi.org/10.1088/0022-3727/49/40/405103
This record's URL: https://www.repository.cam.ac.uk/handle/1810/263778
Attribution 4.0 International, Attribution 4.0 International, Attribution 4.0 International, Attribution 4.0 International