New ytterbium complexes K(Solv)x[Yb(Ln)2] (Solv = ethanol and/or water) with 2-tosylaminobenzylidene-aryloylhydrazones (H2L1, aryloyl = benzoyl; H2L2, aryloyl = 2-naphthoyl) demonstrated high solubility and hole mobility (ca. 2.6 × 10-6 cm2 V-1 s-1), 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 × 10-7vs. 1.7 × 10-6 cm2 V-1 s-1) and a decrease of the quantum yield (1.2% vs. 0.6%). As a result, the optimized OLEDs based on the K[Yb(Ln)2] layer demonstrated efficiencies up to 385 μW W-1 and 441 μW W-1, indicating the superior importance of charge mobility over the quantum yield. These are the highest efficiencies of the Yb electroluminescence.