In order to study the current roll-off in organic light-emitting diodes(OLEDs) under high luminance,the current density versus voltage (J-V)characteristics and the spectra of single-layer and bilayer devices pumped by sources in varied radiation intensities have been observed.The current densities in single-layer device decrease and the spectra shifte towards blue region,since the large amounts of excess anion radicals intensely Absorb the emitted photons to cause the carrier density reduction. In order to ...