An effective intermediate Al/Au electrode for stacked color-tunable organic light emitting devices

Abstract

Bright and efficient stacked color-tunable organic light emitting devices (OLEDs) using an intermediate Al/Au electrode have been reported. The effects of the thicknesses of Al and Au layers on the luminance characteristics have been comprehensively studied. After optimization, the bottom-emission single-unit OLED of 4,4^′,4^′′-Tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine/N,N^′-diphenyl-N,N^′-bis(1-naphthyl)-(1,1^′-biphenyl)-4,4^′-diamine/tris(8-hydroxyquinoline) aluminum has a maximum luminance efficiency (η_L) of 3.37 cd/A by using Al/Au as the cathode and 2.92 cd/A by using Al/Au as the anode. Meanwhile, by introducing the optimized intermediate Al/Au electrode into the stacked color-tunable (red to blue) OLEDs, a red unit with maximum η_L of 4.73 cd/A and a blue unit with maximum η_L of 3.96 cd/A have been obtained. The color can be tuned efficiently along a linear route from pure red with the Commission Internationale de l’Eclairage (CIE) coordinates of (0.662, 0.330) to sky blue with the CIE coordinates of (0.155, 0.340). This scheme can be a potential candidate for achieving high-brightness and efficient stacked color-tunable OLEDs.