We investigated a high-brightness field-emission flat-panel lighting source based on a carbon-nanotube cold cathode. A flat-panel lighting source with a triode structure was fabricated. The maximum luminance of 110 000 cd/m(2) was achieved at a green wavelength at the phosphor screen voltage of 10 kV and a current density of 200 mu A/cm(2). The YAGG:Tb phosphor property under high current density is also discussed. (c) 2008 American Vacuum Society.