Overcoming ultraviolet light instability of sensitized TiO2 with meso-superstructured organometal tri-halide perovskite solar cells

The power conversion efficiency of hybrid solid-state solar cells has more than doubled from 7 to 15% over the past year. This is largely as a result of the incorporation of organometallic trihalide perovskite absorbers into these devices. But, as promising as this development is, long-term operational stability is just as important as initial conversion efficiency when it comes to the development of practical solid-state solar cells. Here we identify a critical instability in mesoporous TiO 2 -sensitized solar cells arising from light-induced desorption of surface-adsorbed oxygen. We show that this instability does not arise in mesoporous TiO 2 -free mesosuperstructured solar cells. Moreover, our TiO 2 -free cells deliver stable photocurrent for over 1,000 h continuous exposure and operation under full spectrum simulated sunlight. Although the performance of sensitized TiO 2 solar cells has increased considerably over recent years, Leijtens et al. show that they are susceptible to a light-driven instability that degrades their performance over time. They go on to show that this instability can be overcome in mesoporous TiO 2 -free devices.