A method for enhancing the light out-coupling efficiency of organic light-emitting devices (OLEDs) has been demonstrated by blending a low-refractive-index polymer, poly(2,2,3,3,3-pentafluoropropyl methacrylate) (PPFPMA), into the emission layer. The resonant wavelength of the weak microcavity devices blueshifted accompanied with a decrease in refractive indices of the light-emitting layers after the addition of PPFPMA. Stronger directed emission toward the surface normal was obtained when the resonant wavelength became closer to the peak wavelength of intrinsic emission spectrum of the organic emitters. The luminous efficiency of the devices was enhanced by more than 20%. The results suggest that the microcavity properties of the OLEDs can be tunable through blending low-refractive-index materials.
- Refractive index