One exemplary embodiment of an electrochromic device comprises a tantalum-nitride ion-blocking layer formed between a transparent conductive layer and an electrochromic layer. Another exemplary embodiment of an electrochromic device comprises a tantalum-nitride ion-blocking layer formed between a transparent conductive layer and a counter electrode. Yet another exemplary embodiment of an electrochromic device comprises a type-2 ion-blocking layer formed on a transparent conductive layer as an ion diffusion barrier overlayer. Still another exemplary embodiment of an electrochromic device comprises a transparent conductive layer formed from tantalum nitride.