Modelling multivalent defects in thin film solar cells

Modeling metastabilities in chalcopyrite-based thin film solar cells

“…(15) and (16), leading to a strong increase of N meas for increasing W. At W ¼ x M , however, the applicable equations change to Eqs. (14) and (17), leading to a sharp drop of N meas . This drop is further enhanced by a smaller decrease of N meas with increasing W because y does not increase as fast with increasing W as when W < x M. In the simulation and measurement results, the drop at 0.5 lm is not as sharp due to the limited resolution of the abscissa, which is always larger than the Debye length.…”

“…It is able to model general multivalent defects. 14 We extended this software to be able to simulate the metastabilities predicted for V Se and In Cu defects in CIGS.…”

Can a multivalent defect be mimicked by several Shockley–Read–Hall-like defects?

“…This implies that the energy levels of the SRH-like defects should be slightly shifted with respect to the corresponding multivalent level, in order to account for possible degeneracy factors. 8,9 The defect density is assumed to be sufficiently low with respect to the shallow doping density, in order to ensure that its influence on the free carrier concentrations is negligible. As will be discussed at the end of the paper, this assumption is not stringent.…”

“…8 The investigated structure represents a Cu͑In,Ga͒͑S,Se͒ 2 -based solar cell and is based on the model "NUMOS CIGS baseline.def," 10 which is distributed together with the installation package of SCAPS. In the absorber a multivalent defect with three possible charge states ͑Ϫ1;0;1͒ has been introduced, leading to two possible transitions ͑Ϫ1/2;1/2͒.…”

“…Finally the results are verified using SCAPS 2.9, a numerical solar cell simulation tool of the University of Gent available to the photovoltaic research community. 7,8 …”