Marked efficiency improvement of a spin-coated phosphorescent pure-white organic light-emitting diode was obtained by incorporating a novel small polymeric nano-dot (PND) in the hole-transporting layer. The resultant device efficiency strongly depended on the concentration and size of the PND used. The resultant power efficiency at 100 cd/m2, for example, was increased from 6.8 to 23.7 lm/W, an increase of 350%, as 14 wt% PND of 8 nm in size was employed. The improvement may be attributed to a better carrier-injection balance resulted from hole trapping on the PND.[All rights reserved Elsevier].