Synthesis of Highly Monodisperse Cu2O Nanocrystals and Their Applications as Hole-Transporting Layers in Solution-Processed Light-Emitting Diodes

The synthesis of phase-pure, narrow-size-distributed and highly stable Cu2O nanocrystals is reported, which can be processed as hole-transporting layers (HTLs) in solution-processed optoelectronic devices. The synthesis is based on a thermal decomposition process with a ligand protection strategy. The reactivity of precursor can be tuned by simply modulating the concentration of oleylamine in non-coordinated solvent, resulting in effectively controlling the size and size distribution of Cu2O nanocrystals. Combined with ligand protection strategy of using lithium stearate and moderate reaction temperature of 170 degrees C, in situ aggregation of Cu2O nanocrystals could be inhibited, exhibiting excellent stability in hexane for several months. The resulting phase-pure colloidal Cu2O particles (after ozone-treatment) were applied as HTLs in polymer light-emitting diodes, the performance of which are comparable to that of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) based devices.