Single-component polyfluorene electrolytes bearing different counterions for white light-emitting electrochemical cells

► Polyfluorene (PF) electrolytes bearing Br−, BF4-, or PF6- counterions were prepared. ► PFs containing BF4- or PF6- counterions showed higher thermal stability. ► The LEC showed a maximum luminescence efficiency of 1.56 lm/W at a low bias of 3 V. ► Pure white emission with CIE'1931 coordinates at (0.33, 0.33) and CRI > 85 was obtained.