We investigated the luminance enhancement, spectral shift and image blur of the OLED with the microlens array
film (MAF) attachment experimentally and theoretically. Higher density, larger curvature, and smaller diameter of the
microlenses extracted more light from the substrate mode. The maximum improvements of the luminance at the normal
direction and the total power were 42.5% (80%) and 45% (85%) from our experimental (simulation) results, respectively.
The differences between the theoretical and experimental results may come from the non-Lambertian radiation of OLED
and the imperfection of the microlens array film. From observing the planar OLED, the peak wavelength is blue-shifted
and the full width at the half maximum (FWHM) decreased with respect to increasing viewing angles due to the
microcavity effect. When the MAF was attached, the spectral peak had a further blue shift (5 to 10 nm at different
viewing angles) compared to that of the planar OLED and it came from the light extraction of the MAF from the
We also quantitatively investigated the "blur width" of the OLED with MAF attachment. Higher image blur was
observed as accompanied with higher extraction efficiency which showed a tradeoff between the image quality and
extraction efficiency. It means that the MAF attachment is more suitable for OLED lighting application, rather than
display application. To reduce the image blur and keep the high extraction efficiency at the same time, we re-designed
the arrangement of the microlens arrays on the film. In our optimized case, we found that the blur width can be reduced
from 79 μm to 9 μm, while the extraction efficiency is kept nearly the same. It shows a possibility to use the microlens
array film on real OLED display for improving the extraction efficiency without image quality degradation.