Abstract: Bismuth-based compounds are gaining increasing attention as a promising class of non-toxic, stable alternatives to lead-halide perovskites for photovoltaics. This is because bismuth is a heavy-metal cation that has demonstrated very little evidence of toxicity and displays electronic similarities to lead. In this talk, I will discuss two promising materials found in the search for bismuth-based perovskite-inspired solar absorbers: bismuth oxyiodide (BiOI) and a double perovskite compound, Cs2AgBiBr6. We show BiOI to be two orders of magnitude more stable in air than methylammonium lead iodide and we achieved 80% external quantum efficiency in photovoltaic devices [1]. In Cs2AgBiBr6, we show using transient absorption spectroscopy that the lifetime of carriers recombining from the band-extrema is 1.4 μs [2]. This exceeds the lifetime of methylammonium lead iodide thin films and suggests that charge transport and extraction can be efficient in solar cells.
[1] R.L.Z. Hoye, et al., Adv. Mater., 2017, 29, 1702176
[2] R.L.Z. Hoye, et al., Adv. Mater. Interfaces, 2018, 5, 1800464
Bio: Dr Robert Hoye is a Royal Academy of Engineering Research Fellow in the Department of Materials Science and Metallurgy at the University of Cambridge, working on the development of semiconductors for optoelectronics. During his PhD (2012-2014), he created an atmospheric pressure chemical vapour deposition reactor that grew oxide semiconductors two orders of magnitude faster than industry-standard atomic layer deposition but at similar temperatures and with similar quality. He was awarded the Jackman prize for best thesis. Dr. Hoye was subsequently a Postdoctoral Research Associate at the Massachusetts Institute of Technology (2015-2016), where he designed new defect-tolerant bismuth-based semiconductors for photovoltaics. His work was awarded a patent and recognised by the US Department of Energy. In 2016, he was the only awardee of the prestigious Nevile Research Fellowship at Magdalene College, Cambridge. In 2018, Dr. Hoye was awarded an early-career fellowship by the Royal Academy of Engineering, which allows him to be a Principal Investigator at Cambridge. His work has been recognised by the American Chemical Society and the Institution of Chemical Engineers. Last year, he was also recognised by the Royal Academy of Engineering with their Young Engineer of the Year prize.