# Dresden 2017 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 8: Photovoltaics

### HL 8.2: Vortrag

### Montag, 20. März 2017, 09:45–10:00, POT 251

**Optoelectronic properties of a-Si:H and a-Si:H/c-Si interfaces from first principles** — •Philippe Czaja^{1}, Urs Aeberhard^{1}, Massimo Celino^{2}, and Simone Giusepponi^{2} — ^{1}IEK-5 Photovoltaics, Forschungszentrum Jülich, Germany — ^{2}ENEA Casaccia, Italy

In order to optimize the optoelectronic properties of novel solar cell architectures, such as the amorphous-crystalline interface (a-Si:H/c-Si) in silicon heterojunction devices, we calculate and analyze the local microscopic structure at the 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.