Fig. 4: Color characteristics of vertically stacked full-color organic light-emitting diodes (OLEDs).

a Normalized electroluminescence spectra for the independently controlled red (R), green (G), and blue (B) OLEDs. b Commission internationale de l’éclairage (CIE) 1931 color coordinates for three, independently controlled R, G, and B OLEDs, under fixed voltage and with other color unit voltage scanning. c Photographic images of vertically stacked full-color OLEDs with various colors.