NEW JOURNAL OF PHYSICS, vol.9, 2007 (SCI-Expanded)
Dual hybridization of highly fluorescent conjugated polymers and highly luminescent nanocrystals (NCs) is developed and demonstrated in multiple combinations for controlled white light generation with high color rendering index (CRI) (> 80) for the first time. The generated white light is tuned using layer-by-layer assembly of CdSe/ZnS core-shell NCs closely packed on polyfluorene, hybridized on near-UV emitting nitride-based light emitting diodes (LEDs). The design, synthesis, growth, fabrication and characterization of these hybrid inorganic-organic white LEDs are presented. The following experimental realizations are reported: (i) layer-by-layer hybridization of yellow NCs (lambda(PL) = 580 nm) and blue polyfluorene (lambda(PL) = 439 nm) with tristimulus coordinates of (x, y) = (0.31, 0.27), correlated color temperature of T-c = 6962K and CRI of R-a = 53.4; (ii) layer-by-layer assembly of yellow and green NCs (lambda(PL) = 580 and 540 nm) and blue polyfluorene (lambda(PL) = 439 nm) with (x, y) = (0.23, 0.30), T-c = 14395K and R-a = 65.7; and (iii) layer-by-layer deposition of yellow, green and red NCs (lambda(PL) = 580, 540 and 620 nm) and blue polyfluorene (lambda(PL) = 439 nm) with (x, y) = (0.38, 0.39), T-c = 4052K and R-a = 83.0. The CRI is demonstrated to be well controlled and significantly improved by increasing multi-chromaticity of the NC and polymer emitters.