First-principles calculations on dislocation-point defect interactions in Cu(In,Ga)Se₂ solar cell absorbers

In Cu(In,Ga)Se₂ based commercial solar cells, power-conversion efficiencies of more than 15% can be achieved, although significant dislocation densities are present. This implies that lattice dislocations in CIGSe-based absorbers are per se electrically inactive or possibly passivated by solute or impurity atoms.
While intrinsic point defects in this material class have been completely characterized by density functional theory calculations using hybrid functionals [1], studying dislocations remains a challenge for electronic structure calculations.
In this talk, I will present a supercell approach using dislocation dipoles, that allows to study study the influence of chemical reconstruction and solute segregation on the electrical activity of mixed dislocations in CISe and CGSe. I will discuss the interaction of various dislocation types with intrinsic [3] and extrinsic point defects [3] and address the importance of mechanical driving forces. Moreover, the computational results are directly compared with experimental data from high-resolution electron microscopy [4].
[1] J Pohl and K Albe, Intrinsic point defects in CuInSe2 and CuGaSe2 as seen via screened-exchange hybrid density functional theory, Phys. Rev. B 87, 245203 (2013)
[2] D Barragan-Yani and K Albe, Atomic and electronic structure of perfect dislocations in the solar absorber materials CuInSe₂ and CuGaSe₂ studied by first-principles calculations Phys. Rev. B 95, 115203 (2017)
[3] D Barragan-Yani and K Albe, Influence of Na and Ga on the electrical properties of perfect 60° dislocations in Cu(In, Ga)Se₂ thin-film photovoltaic absorbers J. Appl. Phys. 123, 165705 (2018)
[4] ES Sanli, D Barragan-Yani, QM Ramasse, K Albe, R Mainz, D Abou-Ras, P v Aken, Point defect segregation and its role in the detrimental nature of Frank partials in thin-film absorbers, Phys. Rev. B 95, 1952093 (2017)