Evaluation and prediction of color-tunable organic light-emitting diodes based on carrier/exciton adjusting interlayer

A color tuning index (ICT) parameter for evaluating the color change capability of color-tunable organic light-emitting diodes (CT-OLEDs) was proposed and formulated. And a series of CT-OLEDs, consisting of five different carrier/exciton adjusting interlayers (C/EALs) inserted between two complementary emitting layers, were fabricated and applied to disclose the relationship between ICT and C/EALs. The result showed that the trend of electroluminescence spectra behavior in CT-OLEDs has good accordance with ICT values, indicating that the ICT parameter is feasible for the evaluation of color variation. Meanwhile, by changing energy level and C/EAL thickness, the optimized device with the widest color tuning range was based on N,N′-dicarbazolyl-3,5-benzene C/EAL, exhibiting the highest ICT value of 41.2%. Based on carrier quadratic hopping theory and exciton transfer model, two fitting ICT formulas derived from the highest occupied molecular orbital (HOMO) energy level and triplet energy level were simulate...