Abstract
The optical absorption of amorphous 
electrochromic display layers is explained as small polaron absorption. The necessary W5+ 5d‐electron localization is favored by the lattice disorder. This is concluded from the change of the optical properties to free‐electron‐like behavior upon crystallization of the layers. The increased electrocoloration stability of amorphous layers and the blue shift of the absorption peak in Mo‐doped 
films can also be explained within the model given.