In photovoltaics, organic-inorganic hybrid perovskites have made a rapid career. But many questions about the crystalline structure of this surprisingly complex class of materials remain unanswered. Now, a team at HZB has used four-dimensional modelling to interpret structural data of methylammonium lead bromide (MAPbBr3), identifying incommensurable superstructures and modulations of the predominant structure. The study is published in the ACS Journal of Physical Chemistry Letters and was selected by the editors as an Editor's Choice.
Solar cells made of crystalline silicon achieve peak efficiencies, especially in combination with selective contacts made of amorphous silicon (a-Si:H). However, their efficiency is limited by losses in these contact layers. Now, for the first time, a team at Helmholtz-Zentrum Berlin (HZB) and the University of Utah, USA, has experimentally shown how such contact layers generate loss currents on the nanometre scale and what their physical origin is. Using a conductive atomic force microscope, they scanned the solar cell surfaces in ultra-high vacuum and detected tiny, nanometre-sized channels for the detrimental dark currents, which are due to disorder in the a-Si:H layer.