Low-temperature-processable amorphous-oxide-semiconductor-based phosphors for durable light-emitting diodes

Abstract

In this study, we fabricated light-emitting diodes (LEDs) on glass substrates at a maximum process temperature of 200 °C using amorphous oxide semiconductor (AOS) materials as emission layers. Amorphous gallium oxide films doped with rare-earth elements (Eu, Pr, and Tb) were employed as AOS emission layers, and the LEDs emitted clear red, green, and pink luminescence upon direct-current application even in the ambient environment. Resonance photoelectron spectroscopy revealed the difference in the electronic structure of the films for each rare-earth dopant, suggesting different emission mechanisms, viz., electron–hole recombination and impact excitation. Although it is widely believed that amorphous materials are unsuitable for use as emission layers of LEDs because of their high concentrations of mid-gap states and defects, the developed rare-earth-doped AOS materials show good performance as emission layers. This study provides opportunities for the advancement of flexible display technologies operating in harsh environments.