Emission spectral stability modification of tandem organic light-emitting diodes through controlling charge-carrier migration and outcoupling efficiency at intermediate/emitting unit interface

An intermediate unit (IMU) of tandem organic light-emitting diode (TOLED) can affect the emission spectral stability because of the different charge-carrier migration and outcoupling efficiency at intermediate/emitting unit interface. In this work, an IMU consisting of carbon 60 and copper(II) phthalocyanine, inserted between red-emitting unit and blueemitting unit, were constructed and fabricated. We focus on the effect of the relative location of the red-emitting unit and blue-emitting unit in the device configuration on the emission spectral stability of TOLED. In the color-Tunable TOLED, a maximum current efficiency of 20.4 cd/A, along with lightemitting spectra tuning from red emission at (0.63, 0.31) according to Commission Internationale de L'Eclairage coordinates at a bias of 10 V to white emission at (0.34, 0.27) at 22 V, is realized. Meanwhile, in the color-stable TOLED, a maximum current efficiency of 15.5 cd/A and a stable white emission at (0.31, 0.27) in a wide range of biases from 12 to 22 V are also obtained. This work might inspire a promising approach for the fabrication of color-Tunable and color-stable OLEDs for both information display and solid-state lighting.