Ytterbium complexes with 2-tosylamino-4-bromobenzylidene-halogenbenzoyhydrazones for highly NIR emitting solution-processed OLEDs

Ytterbium complexes Yb(LX)(HLX) with 2-tosylamino-4-bromobenzylidene-X-benzoylhydrazones (H2LH, X = H; H2LF, X = F; H2LI, X = I) were obtained, their luminescent properties characterized. Halogenation resulted in the increase of solubility (up to 24 g/L in THF) and quantum yield (up to 1.9%). High solubility and high quantum yields resulted in successfully testing these complexes as purely NIR-emitting host-free emitting layers in OLEDs. Surprisingly, among the tested materials the highest efficiency (110 μW/W) was demonstrated by the Yb(LH)(HLH) complex with the lowest quantum yield (0.5%). This efficiency is the highest for the Yb electroluminescence by far, and it was obtained for the solution-processed OLED.