Electrostatic potentials at Cu In,Ga Se2 grain boundaries Experiment and simulations

In the present Letter, we report on a combined ab initio density functional theory calculation, multislice simulation, and electron holography study, performed on a amp; 931;9 grain boundary GB in a CuGaSe2 bicrystal, which exhibits a lower symmetry compared with highly symmetric amp; 931; 3 GBs. We find an electrostatic potential well at the amp; 931;9 GB of 0.8 V in depth and 1.3 nm in width, which in comparison with results from amp; 931;3 and random GBs exhibits the trend of increasing potential well depths with lower symmetry. The presence of this potential well at the amp; 931; 9 GB can be explained conclusively by a reduced density of atoms at the GB. Considering experimental limitations in resolution, we demonstrate quantitative agreement of experiment and theor