Low-Temperature Crystalline Titanium Dioxide by Atomic Layer Deposition for Dye-Sensitized Solar Cells

• Published in: ACS applied materials & interfaces 2013-04, Vol.5 (8), p.3487-3493
• Main Authors: Chandiran, Aravind Kumar, Yella, Aswani, Stefik, Morgan, Heiniger, Leo-Philipp, Comte, Pascal, Nazeeruddin, Mohammad. K, Grätzel, Michael
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/am400866s

Low-temperature processing of dye-sensitized solar cells (DSCs) is crucial to enable commercialization with low-cost, plastic substrates. Prior studies have focused on mechanical compression of premade particles on plastic or glass substrates; however, this did not yield sufficient interconnections for good carrier transport. Furthermore, such compression can lead to more heterogeneous porosity. To circumvent these problems, we have developed a low-temperature processing route for photoanodes where crystalline TiO2 is deposited onto well-defined, mesoporous templates. The TiO2 is grown by atomic layer deposition (ALD), and the crystalline films are achieved at a growth temperature of 200 °C. The ALD TiO2 thickness was systematically studied in terms of charge transport and performance to lead to optimized photovoltaic performance. We found that a 15 nm TiO2 overlayer on an 8 μm thick SiO2 film leads to a high power conversion efficiency of 7.1% with the state-of-the-art zinc porphyrin sensitizer and cobalt bipyridine redox mediator.