Abstract
Quantum dots (QDs)-based white light-emitting diodes (QDs-WLEDs) have been attracting numerous attentions in lighting and flat panel display applications, by virtue of their high luminous efficacy and excellent color rendering ability. However, QDs’ key optical parameters including scattering, absorption and anisotropy coefficients for optical modeling are still unclear, which are severely against the design and optimization of QDs-WLEDs. In this work, we proposed a new precise optical modeling approach towards QDs. Optical properties of QDs-polymer film were obtained for the first time, by combining double integrating sphere (DIS) system measurement with inverse adding doubling (IAD) algorithm calculation. The measured results show that the typical scattering, absorption and anisotropy coefficients of red emissive QDs are 2.9382 mm−1, 3.7000 mm−1 and 0.4918 for blue light, respectively, and 1.2490 mm−1, 0.6062 mm−1 and 0.5038 for red light, respectively. A Monte-Carlo ray-tracing model was set-up for validation. With a maximum deviation of 1.16%, the simulated values quantitatively agree with the experimental results. Therefore, our approach provides an effective way for optical properties measurement and precise optical modeling of QDs for QDs-WLEDs.
Highlights
Colloidal quantum dots (QDs), as emerging nanocrystals light conversion materials, have been attracted more and more attentions in displays and lighting[1,2,3]
If we use above three values in equation (19) as the inputs for the inverse adding-doubling (IAD) algorithm, we should obtain the optical properties a = 0.8, τ = 1, g = 0.8 as a result
In our IAD program, the routine terminates after 145 iteration steps, returning the values of a = 0.7999 and g = 0.8001
Summary
Colloidal quantum dots (QDs), as emerging nanocrystals light conversion materials, have been attracted more and more attentions in displays and lighting[1,2,3]. Unlike the bulk semiconductor material that has a fixed energy gap, the size range of QDs corresponds to the regime of quantum confinement for which electronic excitations feel the presence of the particle boundaries and respond to changes in the particle size by adjusting their energy spectra. While there are difficulties in directly measuring the QDs’ microcosmic parameters such as power dissipation density, wave vector and intrinsic quantum yield et al, making this method impractical to simulate real QDs-polymer film In another approach, Monte-Carlo ray-trace method is performed to theoretically evaluate the performance of QDs-based materials[16,17]. A series of QDs-polymer films samples with varying QDs concentrations were fabricated, and their transmittance, reflectance and collimating transmittance were measured by the DIS system Their optical properties of scattering coefficient, absorption coefficient and anisotropy coefficient were calculated by the IAD algorithm. These parameters were adopted in Monte-Carlo ray-tracing model to conduct the simulation, and the ray-tracing results were compared with the experimental results to validate the feasibility of our model
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