New mercury-free Flat Fluorescent Lamps (FFLs) with a different kind of phosphor layers were fabricated in order to investigate the effects of electrons with the surplus energy on the electro-optical characteristics. Discharge characteristics of the FFLs were compared as functions of the gas pressure and the mixture ratios, and with or without phosphor layer on the front plate. The experimental results revealed that FFLs with the PL (Photoluminescence) phosphor layer on the front and the rear plates show the highest luminance. However, it is found that the difference of luminance between FFLs with the CL (Cathodoluminescence) phosphor layer and FFLs with the PL phosphor on the front plate is considerably decreased in the cases of the gas pressure below 50 Torr and the discharge cell with a cell depth of 0.8 mm, indicating that the electrons play a role in the excitation of the phosphor under a certain discharging condition.