In this study, Eu-doped polyvinylidene fluoride nanofibers (PVDF NFs) were fabricated by an electrospinning method and applied as an active layer in triboelectric nanogenerators (TENGs). Structural and optical investigations showed that Eu3+ was successfully doped in the PVDF NFs and it induced discrete emissions corresponding to the electronic transitions. As the Eu content increased, the phase transformation was enhanced from the alpha-phase to the beta-phase in the PVDF NFs, and their diameter decreased. These changes enhanced the electrical output power of the TENGs. However, the further addition of Eu resulted in precipitation of the NO3--related complex on the surface of the PVDF NFs, which was detrimental to performance of the TENGs. Due to these conflicting effects, the output power increased from 13 to 26 mu W/cm(2) as the Eu contents increased from 0 to 2.7 wt%, whereas it decreased drastically to 4.9 mu W/cm(2) when the Eu content increased further to 5.3 wt%. Therefore, the optimum amount of Eu doping has advantageous effects.