Fig. 1. (Color online) (a) Schematic illustration of the 1,8-diaminooctane ligand treatment process, (b) chemical structure (top) and graphical sketch (bottom) of the oleic acid and 1,8-diaminooctane ligand. The purple and blue balls represent the carboxyl and amine groups, respectively, and the green line is the carbon chain.

Fig. 2. (Color online) Characterization of the QD films. (a) UV-vis absorption spectra, (b) PL spectra and (c) time-resolved PL decay of the QD films before and after ligand treatment. The inset of (b): the corresponding PL image of the QD films under 365 nm LED excitation. (d) The PL spectra of the pristine and ligand-treated QD films rinsed with CB. The inset of (d): PL image (under 365 nm) of corresponding PL image of the QD films.

Fig. 3. (Color online) SEM images of the (a) pristine QD film and (b) ligand-treated QD film. AFM images of the (c) pristine QD film and (d) ligand-treated QD film.

Fig. 4. (Color online) Device characteristics of inverted QLED. (a) Device structure, (b) J–V–L characteristics, (c) EQE–J characteristics, and (d) EL spectra of the inverted device (at 8 V).

Fig. 5. (Color online) Capacitance–voltage characteristics of the inverted devices, f = 1 kHz.