The counter anionic size effects on electrochemical, morphological, and luminescence properties of electrochemically deposited luminescent films

Luminescent films electrodeposited (ED) on indium tin oxide glass are considered for application in low-cost luminescent devices. During ED processes, the anions play an important role in the quality of resultant ED films. Three species of supporting electrolytes TBA-X (TBA=n-tetrabutylammonium, X=BF4-, PF6-, and AsF6-) with different size of anions were used for the preparation of ED films from a branched carbazyl luminescent precursor TCPC. Increasing the size of anions (BF4-< PF6-< AsF6-) resulted in an increase of growth rate and improved the morphology of ED films. The ED film prepared using TBA-AsF6 as supporting electrolyte showed strong fluorescence with efficiency of 65%, which was significantly higher than that of ED films from the smaller anions BF4- and PF6-. By utilizing the ED films as emitting layer, the light-emitting device also showed improved performance with increasing size of anions in the electrolytes. The origin of observed counter anionic size effects on electrochemical, morphological, and luminescent properties of ED films can be attributed to the difference in interaction between the carbazyl cation and anions, which induced an easier (i.e., for the larger size ions) or difficult (i.e., for the smaller size ions) dedoping process. (C) 2008 The Electrochemical Society.