Electron transport layer composition for inkjet printing and method for preparing same

A light-emitting device, comprising:

• a first electrode;
• a second electrode disposed to face the first electrode;
• an emission layer disposed between the first electrode and the second electrode;
• a hole transport layer disposed between the first electrode and the emission layer;
• and
• an electron transport layer disposed between the emission layer and the second electrode, the electron transport layer comprising:
• metal oxide nanoparticles;
• and
• at least three solvents that differ in terms of at least one of viscosity, polarity, or vapor pressure;
• wherein the electron transport layer has a viscosity of 1.0 to 3.0 cps at 20° C. a vapor pressure of 0.6 to 45 mmHg at 20° C., a contact angle of 25 to 80°, and a solid content of 5 to 30 wt %.

A method for preparing an electron transport layer composition for inkjet printing, the method comprising:

• a first step of adding a basic substance to a reaction solution, in which a zinc-containing compound and a compound containing a metal capable of increasing a ZnO band gap are dissolved, followed by precipitation, thereby preparing a metal oxide nanoparticle dispersion;
• and
• a second step of adding, to the prepared metal oxide nanoparticle dispersion, the at least three solvents that differ in terms of at least one of viscosity, polarity, or vapor pressure, followed by mixing, thereby preparing the electron transport layer composition;
• wherein the electron transport layer composition has a viscosity of 1.0 to 3.0 cps at 20° C. a vapor pressure of 0.6 to 45 mmHg at 20° C. a contact angle of 25 to 80°, and a solid content of 5 to 30 wt %.