Numerical Investigations and Analysis of Cu₂ZnSnS₄Based Solar Cells by SCAPS-1D

Abstract

This paper reports numerical investigation, using SCAPS-1D program, of the influence of Cu 2 ZnSnS 4 (the so-called CZTS) material features such as thickness, holes, and defects densities on the performances of ZnO:Al/i-ZnO/CdS/CZTS/Mo solar cells structure. We found that the electrical parameters are seriously affected, when the absorber thickness is lower than 600 nm, mainly due to recombination at CZTS/Molybdenum interface that causes the short-circuit current density loss of 3.6 mA/cm 2 . An additional source of recombination, inside the absorber layer, affects the short-circuit current density and produces a loss of about 2.1 mA/cm 2 above this range of absorber thickness. The<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>J</mml:mi><mml:mtext>-</mml:mtext><mml:mi>V</mml:mi></mml:math>characteristic shows that the performance of the device is also limited by a double diode behavior. This effect is reduced when the absorber layer is skinny. Our investigations showed that, for solar cells having a CZTS absorber layer of thin thickness and high-quality materials (defects density ~10 15 cm −3 ), doping less than 10 16 cm −3 is especially beneficial. Such CZTS based solar cell devices could lead to conversion efficiencies higher than 15% and to improvement of about 100 mV on the open-circuit voltage value. Our results are in conformity with experimental reports existing in the literature.