White light generation tuned by dual hybridization of nanocrystals and conjugated polymers

Abstract

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 (λPL = 580nm) and blue polyfluorene (λPL = 439 nm) with tristimulus coordinates of (x, y) = (0.31, 0.27), correlated color temperature of Tc = 6962 K and CRI of R a = 53.4; (ii) layer-by-layer assembly of yellow and green NCs (λPL = 580 and 540 nm) and blue polyfluorene (λPL = 439 nm) with (x, y) = (0.23, 0.30), Tc = 14395 K and Ra = 65.7; and (iii) layer-by-layer deposition of yellow, green and red NCs (λPL = 580, 540 and 620 nm) and blue polyfluorene (λPL = 439 nm) with (x, y) = (0.38, 0.39), T c = 4052 K and Ra = 83.0. The CRI is demonstrated to be well controlled and significantly improved by increasing multi-chromaticity of the NC and polymer emitters.