Outcoupling-enhanced organic light-emitting diodes using simple phase-separated polymer films

A high-performance external light outcoupling film for organic light-emitting diodes (OLEDs) is developed using a novel phase-separated polymer (PSP) which is spontaneously formed from a homogeneous solution of poly(amic acid) and polyimide in dimethylacetamide. The phase separation during the spin-coating process leads to complex morphologies of film with random microdent and nanobump patterns by a self-assembly of polymers. The PSP film is utilized on the backside of a glass substrate in green OLEDs as a light outcoupling film, leading to a considerable enhancement of light outcoupling efficiency. Both the current efficiency and power efficiency of OLEDs with the PSP film are improved by a factor of 1.45 and 1.53, respectively, in comparison with those of the reference device. The results demonstrate that the PSP film could serve as a promising outcoupling film for OLEDs.