Decisive for the solar cell efficiency is being able to control the deposition process of the perovskite crystallites within the nanoporous electrode, which is comprised of metal oxides and micronized graphite. New is the process used by the Fraunhofer researchers to fill the otherwise completed cell with perovskite and the subsequent crystallization. While the processes up to now led to uncontrolled crystal growth, the researchers around Hinsch have found a way to convert the perovskite to a molten salt at room temperature using a polarized gas, and so were able to fill the pores of the electrode. The final desorption of the gas greatly increases the melting point and brings about the crystallization. The result is a homogenous growth process. Photoactive layers manufactured in this manner show a high photovoltage of 1 volt and have led to the certified stable solar efficiency of 12.6 % for in-situ laboratory cells (0.1cm²) with graphite electrodes. The Fraunhofer scientists expect further efficiency improvements for their printed in-situ perovskite solar cells, not least because the perovskite material already has demonstrated efficiencies up to 22 %, as evidenced in the scientific papers on non-scalable laboratory cells.
