Achievement and mechanism of large-scale color tunable OLEDs based on interfacial charge transfer complexes with dual donors

Color tunable organic light-emitting diodes have intrigued many application fields, such as smart lighting and information encryption. In this study, we propose a simple structure based on interfacial charge transfer complexes (CTCs) with double donors and single acceptors for achieving color tunability. Through embedding a second donor between the primary donor and the acceptor, the emission of devices can be well-tuned by simply controlling the applied voltage. The calculated frontier molecular orbitals of constituted monomers and heterodimers via density function theory confirm the formation of CTCs between the donors and acceptor. Importantly, the highest occupied molecular orbital level and charge carrier mobility of the second donor are crucial to realize widely adjustable spectra with the voltage. With this strategy, the device incorporating 1,3-di(9H-carbazol-9-yl)benzene as the second donor and 4,4′,4″-tris[(3-methylphenyl)phenylamino] triphenylamine as the primary donor exhibits the largest color shift. The CIE coordinates span from (0.52, 0.46) at 4 V to (0.29, 0.26) at 10 V. These findings shed light on the fact that the double-donor-strategy is feasible for fulfilling large-scale color tunability of CTC-based organic light-emitting diodes and is beneficial to simplify the fabrication process.