Record efficiency of 1000 nm electroluminescence from a solution-processable host-free OLED.

New ytterbium complexes K(Solv)[Yb(L)] (Solv = ethanol and/or water) with 2-tosylaminobenzylidene-aryloylhydrazones (HL, aryloyl = benzoyl; HL, aryloyl = 2-naphthoyl) demonstrated high solubility and hole mobility ( 2.6 × 10 cm V s), while their electron mobility and PLQY were different. The substitution of a benzoyl substituent with naphthoyl resulted in a significant increase of the electron mobility (6.9 × 10 1.7 × 10 cm V s) and a decrease of the quantum yield (1.2% 0.6%). As a result, the optimized OLEDs based on the K[Yb(L)] layer demonstrated efficiencies up to 385 μW W and 441 μW W, indicating the superior importance of charge mobility over the quantum yield. These are the highest efficiencies of the Yb electroluminescence.