Photoelectrochromic Devices with Enhanced Power Conversion Efficiency.

In the present work, we propose a new architecture for partly covered photoelectrochromic devices with a modified anode layout, so that the TiO film is deposited first on the substrate, covering a small part of its surface, followed by the WO film that covers the remaining device area. As a result, the TiO film can be subjected to the proper thermal and chemical treatment without affecting the electrochromic performance of the WO film. The proposed design led to photoelectrochromic (PEC) devices with a power conversion efficiency (PCE) four times higher than that of typical partly covered devices, with a measured maximum of 4.9%. This, in turn, enabled a reduction in the total area covered by the photovoltaic unit of the devices by four times (to 5% from 20%), thus reducing its visual obstruction, without affecting the depth, uniformity and speed of coloration. A detailed study of the parameters affecting the performance of the new devices revealed that, with the cover ratio decreasing, PCE was increasing. The photocoloration efficiency also exhibited the same trend for cover ratio values below 15%. Storage of the devices in short circuit conditions was found to accelerate optical reversibility without affecting their photovoltaic and optical performance.