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N. Severino, N. Bednar, N. Adamovic:
"Guidelines for optimization of the performances of CIGS thin film solar cells";
Talk: 3rd Euro-Mediterranean Conference on Materials and Renewable Energies - EMCMRE-3, Marrakech, Morocco; 11-02-2015 - 11-06-2015; in: "3rd Euro-Mediterranean Conference on Materials and Renewable Energies - EMCMRE-3", (2015).

In this work we present the design rules for Cu(In,Ga)Se2 (CIGS) solar cells with a goal to
better understand and analyze the relations between the solar cell material parameters and the
key output solar cell performance. This study will support researchers as well as
manufacturers to optimize both the fabrication technology and different cell parameters in
order to reach high efficiency solar cells. Among the thin-film technologies, solar cells based
on Cu(In,Ga)Se2 absorber material are one of the most promising, since CIGS is a direct band
gap semiconductor characterized by a high absorption coefficient. Moreover the band gap of
this semiconductor has a unique characteristic since it can be graded over a wide range by
changing the gallium (Ga) concentration in the thin film layer, which greatly affects the
efficiency of the solar cell. The developed numerical model showed a good confirmation with
the experimental results. In particular, we present the dependence of key output cell
parameters (e.g. 1-V curve, EQE curve, maximum output power, fill factor, Jsc, Voc) on the
Ga profile, energy gap, electron affinity, density, type and position of defects, density of states
in both conduction band and valence band, acceptor and donor density for CIGS (absorption
layer) and CdS (buffer layer), as well as the thickness of each solar cell layer. The dependence
of the solar cell electrical properties on the amount of Ga and its doping profile was observed
in order to improve the transport properties of photo-generated carriers and a strategy for an
improved Ga profile was proposed in order to enhance the performances of CIGS devices.
Furthermore, promising results were obtained analyzing the possibility to use few alternative
Cd-free buffer layers (Zn2Sn04, InS and ZnS) in place ofthe standard CdS. Acknowledgment:
This work has been supported by the Austrian Research Promotion Agency FFG through the
project SynerCIS, project No. 840706, and also by the European Commission FP7-NMP
Programme project SolarDesign, under the grant agreement No. 310220.

In this work we present the design rules for Cu(In,Ga)Se2 (CIGS) solar cells with a goal to
better understand and analyze the relations between the solar cell material parameters and the
key output solar cell performance. This study will support researchers as well as
manufacturers to optimize both the fabrication technology and different cell parameters in
order to reach high efficiency solar cells. Among the thin-film technologies, solar cells based
on Cu(In,Ga)Se2 absorber material are one of the most promising, since CIGS is a direct band
gap semiconductor characterized by a high absorption coefficient. Moreover the band gap of
this semiconductor has a unique characteristic since it can be graded over a wide range by
changing the gallium (Ga) concentration in the thin film layer, which greatly affects the
efficiency of the solar cell. The developed numerical model showed a good confirmation with
the experimental results. In particular, we present the dependence of key output cell
parameters (e.g. 1-V curve, EQE curve, maximum output power, fill factor, Jsc, Voc) on the
Ga profile, energy gap, electron affinity, density, type and position of defects, density of states
in both conduction band and valence band, acceptor and donor density for CIGS (absorption
layer) and CdS (buffer layer), as well as the thickness of each solar cell layer. The dependence
of the solar cell electrical properties on the amount of Ga and its doping profile was observed
in order to improve the transport properties of photo-generated carriers and a strategy for an
improved Ga profile was proposed in order to enhance the performances of CIGS devices.
Furthermore, promising results were obtained analyzing the possibility to use few alternative
Cd-free buffer layers (Zn2Sn04, InS and ZnS) in place ofthe standard CdS. Acknowledgment:
This work has been supported by the Austrian Research Promotion Agency FFG through the
project SynerCIS, project No. 840706, and also by the European Commission FP7-NMP
Programme project SolarDesign, under the grant agreement No. 310220.