Different colors of polymer light-emitting diodes can be obtained by changing the active layer using different strategies: mixture of different conjugated polymer forming polymer blends, mixtures of polymer and dyes, quantum dots, nanorods ou nanotubes, materials forming excimers or exciplexes, etc. The chemical structures of these materials define the band gap and, in some cases, the color of the emission can be influenced by the morphology of the polymer film and by energy transfer processes among the components. Due to the dependence of the color on the chemical structure of the materials, substantial efforts have been done in synthetic processes of new materials. In a recent work [1] we demonstrate that white color emission might be generated in a diode composed by one component EL layer of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(9,9-di-(5´-pentanyl-fluorenyl-2,7
-diyl)] (PFOFPen) and an external photoluminescent layer of MEH-PPV. Using the same strategy, a diode with one active layer of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl] (F8BT) and with external layer of a water soluble plastic film of poly(vinyl alcohol) (PVA) containing xanthene dyes (eosin B - EB, erythrosine B – ErB and Rose Bengal - RB). Changes of the CIE color coordinates depend on the dyes and on the thickness of the external PL layer. For example, in the case of PVA/RB with 59 µm thick, the CIE coordinates are [0.403,0.55] and whereas for the F8BT these coordinates are [0.352,0.592]. This methodology used here for external dyes is very adaptable to other pairs of EL/PL systems, as we showed previously for the PFOFPen/MEH-PPV EL/PL system. [1]F. J. Quites, G. C. Faria, T. D. Z. Atvars, Mat. Lett. 130(2014), 65-67.