editorial A decade of This year marks ten years of organic–inorganic perovskite research. Now, after achieving remarkable gains in performance, applications are starting to make their way out of research laboratories into the real world.

n 2009, Tsutomu Miyasaka and colleagues gallium selenide, although they lag behind the market in the coming years. Indeed, a in Japan reported on organic–inorganic silicon photovoltaics, which hold a 26.6% number of companies and research centres lead halide perovskite compounds as light record efficiency. At the time of writing, are devoted to technology transfer from I 1 absorbers in dye-sensitized solar cells . the record perovskite power conversion laboratory to market, working on device Although the properties of these materials efficiency, reported by the Chinese Academy stability and reliability, up-scaling and had been investigated for many years and of Sciences in late 2018 and certified by the compatibility of the cell manufacturing applications such as light-emitting diodes National Renewable Energy Laboratory, with industrial processes, such as roll- had been reported by Chondroudis and is 23.7% (ref. 6). Furthermore, small lab- to-roll deposition. Mitzi in the United States2, the work of scale cells have been scaled up to large-area Beyond multi-junction solar cells, Miyasaka and team was the first to make use devices (>​1 cm2) and modules (>​10 cm2), building-integrated photovoltaics is of perovskites for solar energy applications. while employing deposition methods another promising application. Saule However, as the device delivered just 3.8% compatible with industrial manufacturing. Technologies has recently completed a pilot power conversion efficiency, had an active Finally, perovskite solar cells have also installation of semi-transparent perovskite area of 0.24 cm2 and was stable for only a now been demonstrated to be stable for photovoltaic devices into an office building few minutes, these initial results presented thousands of hours under conditions that façade in Poland7. Additionally, perovskite uncertainties about the likely deployment of should mimic those that a real device can solar cells could be even more versatile: these materials in photovoltaics. be exposed to. recent lab-based results show interesting Nevertheless, given their interesting Nevertheless, the lack of consistency performance under both concentrated optoelectronic properties, research forged in the stress factors used for assessing and low-light intensities as well as good ahead and a few years later some seminal the stability of the devices has urged radiation tolerance, which are relevant to publications appeared. In 2012, the groups of the perovskite community to identify concentrator, indoor and space applications, Michael Grätzel in Switzerland and Nam-Gyu degradation mechanisms and define test respectively. But there is more to perovskites Park in South Korea3 demonstrated solid- protocols that are specific for perovskites than photovoltaics: other perovskite-based state perovskite photovoltaic devices that and would complement the specifications applications, such as light-emitting diodes, overcame the poor stability of the material in of standards defined by the International detectors, lasers and photocatalysts, have liquid-based dye-sensitized solar cells. Later Electrotechnical Commission for been reported to hold great potential. in the same year, Henry Snaith and colleagues photovoltaic technologies. Energy is Yet for all these major advances, topical in the United Kingdom demonstrated that always on the lookout for these advances and challenges still remain. These include the materials are not only able to sensitize seeks to support such endeavours wherever device stability under realistic operational a semiconductor, but also, and more we can. Several such examples have been conditions, the environmental impact of interestingly, can themselves transport reported in our pages before. More widely, the modules with concerns around lead and electronic charges to the solar cell electrodes, year by year, we have been gathering what tin still being debated, the efficiency loss enabling higher device efficiencies4. Organic– we consider to be the most relevant research when upscaling to large-area devices, and inorganic lead halide perovskites thus developments published across Nature remaining gaps in the fundamental materials became the front runners among emerging Research journals in our ‘Perovskites for . Encouragingly enough though, photovoltaic materials and the field has optoelectronics’ collection (https://www. while silicon will keep dominating the advanced dramatically ever since. nature.com/collections/fnnxcznnbb). photovoltaic market, perovskite solar cells Over the years, the perovskite community The remarkable developments on single- seem likely to soon appear in commercial has put great efforts into addressing the junction perovskite solar cells over the past tandem solar cells and as building-integrated peculiar physics and chemistry of these decade have also fuelled research on two- photovoltaic elements. We look forward to materials. For instance, the first Materials junction (or ‘tandem’) structures, where many more years of exciting discovery from Research Society (MRS) symposium perovskite cells are coupled with other these materials. ❐ entirely dedicated to perovskite solar cells — photovoltaic technologies. In 2018, Oxford organized within the 2014 MRS fall meeting PV, a UK-based company, announced — discussed the causes of hysteresis in the a monolithic perovskite/silicon tandem Published online: 14 January 2019 current–voltage curves, the nature of charge solar cell with a certified 28.0% power https://doi.org/10.1038/s41560-018-0323-9 traps, defects and grain boundaries, as well as conversion efficiency, outperforming both References ion migration, all of which posed threats to perovskite and silicon single-junction solar 1. Kojima, A. et al. J. Am. Chem. Soc. 131, 6050–6051 (2009). 6 device stability and played a role in hampering cells . This should be compared with the 2. Chondroudis, K. et al. Chem. Mater. 11, 3028–3030 (1999). device efficiency5. From there, striking current efficiency record for tandem solar 3. Kim, H. S. et al. Sci. Rep. 2, 591 (2012). progress has been made on the perovskite cells of 32.8%, held by LG Electronics for 4. Lee, M. M. et al. Science 338, 643–647 (2012). 5. Egger, D. A. et al. J. Phys. Chem. Lett. 6, 279–282 (2015). layer quality and device performances. gallium indium phosphide/gallium arsenide 6. Best Research-Cell Efciencies (NREL, accessed 02 January Quite remarkably, perovskite solar cells monolithic devices, which are less cost 2019); https://www.nrel.gov/pv/assets/pdfs/pv-efciency- currently outperform the efficiency of more effective than perovskites or silicon. This chart.20181221.pdf 7. Saule Technologies and Skanska change construction industry. established photovoltaic technologies such remarkable result sets great expectations Saule Technologies https://sauletech.com/2018/12/13/saule- as cadmium telluride and copper indium for perovskite-based tandem cells to enter technologies-and-skanska-change-construction-industry (2018).

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