Fig. 1. Sketch of interfacial delamination in thin film electrochromic devices.

a The mechanical delamination from the current collector limits electron and counterion transport and impedes chromic switch of the film upon electrochemical cycles. b Experimental observation of mechanical breathing of PProDOT film and its morphology after every 60 cycles. The thin film experiences repetitive expansion and shrinkage in volume in the redox reactions which ultimately leads to the failure of the device at the interface.