ProGB · Property transformation of Grain Boundaries

Property transformation of grain boundaries (ProGB) is a challenge and a big opportunity. Besides being indispensable in many semiconductor compounds, grain boundaries (GBs) are found to be often detrimental in most bulk and thin-film solar cells limiting devices’ efficiency. This is because understanding how the detrimental properties can be intentionally transformed remains difficult and often impossible. Therefore, ProGB aims to understand and even transform the GBs properties on the nanoscale by employing a novel approach. This approach consists of three steps with three objectives. (1) It will explore the GBs' intrinsic properties and the properties transformation down to the nanoscale in semiconductor prototypes through a new platform specially developed for GB characterization. It will (2) understand the impact of GBs’ structure and stoichiometry on the electronic properties down to the nanoscale and (3) utilize the experimental evidence and the concepts gained to obtain high-performance photovoltaic and electronic devices.Finally, ProGB will employ a unique infrastructure that will be implemented and established in the PI’s team. It will apply atom probe tomography as a principal technique to determine the composition of GBs in Si (as a typical prototype material) and in AgBiS2 (as a novel material for ultrathin-film solar cell applications), combined with techniques to determine the materials’ electronic and structural properties on exactly the same position on the sample. In this way, ProGB can realize a true 1:1:1 correlation with unprecedented precision in material characterization. These experimental observations will be consolidated by theoretical simulations and device modeling. Last but not least, the outcome of ProGB will rescue thin-film technology with polycrystalline absorbers and will be of big benefit to the latest technologies such as tandem and ultrathin-film solar cells.