Electrodeposition of Simonkolleite as a Low-Temperature Route to Crystalline ZnO Films for Dye-Sensitized Solar Cells

A pulsed electrodeposition procedure has been developed to prepare macroporous films of the semiconducting mineral simonkolleite, Zn 5 (OH) 8 Cl 2 ·H 2 O, on glass/FTO substrates. The morphology is characterized by the presence of smooth, micron-sized hexagonal platelets, and relatively thick films of 6 μ m can be prepared in about 15 min. Simonkolleite can be transformed into crystalline, mesoporous ZnO using a relatively low temperature thermal treatment (250 °C). While the macrostructure of hexagonal platelets is maintained, they become mesoporous due to the removal of water and Cl − -containing reaction products. Dye-sensitized solar cells were fabricated with both simonkolleite and ZnO films, using the recently reported fully organic benzothiadiazole-based photosensitizer MG-207, and an electrolyte solution based on either the I − /I 3 − or the Co(bpy) 3 2+/3+ redox couple. An efficiency of 1.74% has been obtained for ZnO/MG-207/Co(bpy) 3 2+/3+ solar cells, illustrating the promise of crystalline, mesoporous ZnO obtained via a low-temperature simonkolleite route for portable and lightweight devices based on flexible substrates.