Flat-panel light source with lateral-gate triode structure and urchin-like α-Fe2O3 microspheres as field emitters

Urchin-like α-Fe2O3 microspheres (radial α-Fe2O3 nanowires on α-Fe2O3 microspheres) are used as field emitters for a flat-panel lighting device with a lateral-gate-electrode structure. The urchin-like α-Fe2O3 microspheres are in situ grown on the cathode electrode via thermal oxidation at 350 °C for 12 h after the screen-printing of pattern Fe microspheres on the cathode electrode. The lateral-gate triode structure comprises an Ag cathode and a pair of Ag gate electrodes screen-printed laterally on both sides of the cathode. The role of the gate electrodes is to enhance the emission current and increase luminance uniformity and that of the anode electrode is to control the luminance intensity. The radial nanowire emitters on the spheres ensure good field emission performance without any pretreatment and in situ growth of the material enhances the contact between the electrode and the material. The microspheric emitters and the lateral-gate structure, which covers a small part (4.32%) of the printed area over the entire panel (3.5 cm × 5 cm) leads to, high luminance, excellent luminance uniformity and tunable luminance characteristics of the field-emission light source. A maximum luminance of 8330 cd/m2 and a luminance uniformity of 92.4% are achieved with a gate voltage of 500 V, an anode voltage of 4000 V, and the anode current of 1.32 mA.