  Traditional solid-state lighting relies on color converters with a serious
environmental footprint. As an alternative, natural materials such as plant
extracts could be employed if their low quantum yield (QYs) in liquid and solid
states were higher. With this motivation, here, we investigate the optical
features of P. harmala extract in water, develop its efficient color-converting
solids using a facile, sustainable, and low-cost method, and integrate it with
a light-emitting diode. To obtain a high-efficiency solid host for the P.
harmala-based fluorophores, we optically and structurally compared two
crystalline and two cellulose-based platforms. Structural characterizations
indicate that sucrose crystals, cellulose-based cotton, and paper platforms
allow fluorophores to be distributed relatively homogenously as opposed to the
KCl crystals. Optical characterizations reveal that the extracted solution and
the extract-embedded paper possess QYs of 75.6% and 44.7%, respectively,
whereas the QYs of the cotton, sucrose, and KCl crystals remain below 10%.
Subsequently, as a proof-of-concept demonstration, we integrate the as-prepared
efficient solid of P. harmala for the first time with a light-emitting diode
(LED) chip to produce a color-converting LED. The resulting blue-emitting LED
achieves a luminous efficiency of 21.9 lm/Welect with CIE color coordinates of
(0.139,0.070). With these results, we bring plant-based fluorescent
biomolecules to the stage of solid-state lighting. We believe that they hold
great promise as next-generation, environmentally friendly organic color
converters for lighting applications.
