Ab initio Description of Optoelectronic Properties at Defective Interfaces in Solar Cells

TL;DR

This paper uses ab initio methods to analyze the microscopic structure and electronic properties of defective interfaces in silicon-based solar cells, aiming to improve understanding of defect states and optoelectronic behavior.

Contribution

It introduces a combined molecular dynamics, density functional theory, and GW approach to characterize defect states at amorphous-crystalline silicon interfaces in solar cells.

Findings

Identification of localized defect states affecting recombination.

Quasi-particle corrections can be approximated by scissors shifts.

Insights into the impact of material inhomogeneities on electronic properties.

Abstract

In order to optimize the optoelectronic properties of novel solar cell architectures, such as the amorphous-crystalline interface in silicon heterojunction devices, we calculate and analyze the local microscopic structure at this interface and in bulk a-Si:H, in particular with respect to the impact of material inhomogeneities. The microscopic information is used to extract macroscopic material properties, and to identify localized defect states, which govern the recombination properties encoded in quantities such as capture cross sections used in the Shockley-Read-Hall theory. To this end, atomic configurations for a-Si:H and a-Si:H/c-Si interfaces are generated using molecular dynamics. Density functional theory calculations are then applied to these configurations in order to obtain the electronic wave functions. These are analyzed and characterized with respect to their localization and their contribution to the (local) density of states. GW calculations are performed for the a-Si:H configuration in order to obtain a quasi-particle corrected absorption spectrum. The results suggest that the quasi-particle corrections can be approximated through a scissors shift of the Kohn-Sham energies.