Comparison of UV Irradiation and Sintering on Mesoporous Spongelike ZnO Films Prepared from PS- b-P4VP Templated Sol-Gel Synthesis

Mesoporous ZnO films with large surface-area-to-volume ratio show great promise in multiple applications, among which solid-state dye-sensitized solar cells (ssDSSCs) have attracted great attention in the field of photovoltaics. An appropriate mesopore size in the nanostructured ZnO films significantly plays an indispensable role in improving the device efficiency that resulted from an efficient penetration of dye molecules and solid hole transport material. In the present work, mesoporous spongelike ZnO films are prepared using sol-gel synthesis templated by a diblock copolymer polystyrene-block-poly(4-vinylpyridine). Two different template removal techniques, ultraviolet (UV) irradiation and high-temperature sintering, are used to compare their respective impact on the pore sizes of the final ZnO thin films. Both the surface morphology and the inner morphology show that mesopores obtained via UV irradiation are smaller as compared to their sintered counterparts. Moreover, increasing the template-to-ZnO precursor ratio is found to further enlarge present mesopores. Accordingly, a strong correlation between the pore sizes of sol-gel synthesized ZnO films and photovoltaic performance of fabricated ssDSSCs is demonstrated. In contrast with the devices fabricated from the UV-irradiated ZnO films, those obtained from sintered samples show >2 times higher efficiency.