Discharge characteristics of mercury-free flat fluorescent lamps with various electrode configurations analysed through a two-dimensional fluid model simulation

The discharge characteristics and factors related to the luminous efficacy of mercury-free flat fluorescent lamps (MFFLs) with three different types of coplanar, counter and combination electrode configurations were studied via a two-dimensional numerical simulation. The spatiotemporal distributions of the potential, electric field, electron density, Xe** density and current waveforms of the MFFLs were obtained and analysed. The MFFL with the combination electrode configuration shows the highest vacuum ultraviolet (VUV) efficacy value. The vertical electrode in the MFFL with the combination electrode configuration prevents the electric field at the gap space from decreasing rapidly, and extends the discharge path. The effects of the vertical electrode help one to increase the Xe excitation efficacy. In addition, a new auxiliary electrode was proposed in the original MFFL with the combination electrode configuration. The MFFL with the new auxiliary electrode has broader distributions of electrons and Xe** species, and a higher VUV efficacy value than the original MFFL with the combination electrode configuration at the same voltage.