Perovskite Solar Cells in the Public Domain as the Community Gears Up for Technical Advances

Metal-halide perovskites have seen the fastest rise in power conversion efficiency ever witnessed by any photovoltaic technology. To cite a recent conversation we had with Michael Gratzel, a major player in the ? perovskite field, the efficiency increase was a "meteoric rise to 22% f rom a little bit over 3% in just a few years" and "a kind of gold rush." 1 Along with the increase in efficiency, several outstanding perovskite properties have been brought to light with specialized experiments and simulations. These efforts in turn have provided the scientific basis to the explore underlying principles of solar cell efficiency. As thin-film fabrication methods are being streamlined, the intrinsic limit of optoelectronic properties are now being explored also for other applications. For example, the reported values of carrier diffusion length, which plays a central role in solar cell devices allowing efficient charge collection at selective contacts, steadily increased over time to current values of several micrometers. These surprising results were the topic of debate at major scientific forums. The ongoing discussions also highlighted how the peculiar lead-halide combination gives rise to a unique set of material properties (e.g., defect tolerance, spin-orbit and Rashba effects, large polarons, hot carriers, etc.) that are likely at the heart of the perovskite success.