Boost the Efficiency of Cu2ZnSn(S,Se)4 Solar Cell by Using Mn2+‐Induced Ultrathin CdS Buffer Layer

In this article, the efficiency of CZTSSe solar cell is improved by adding manganese chloride in the deposition solution of the CdS buffer layer. The mechanisms behind the experimental results are investigated. On one hand, the MnCl2 can facilitate the deposition of an ultrathin (≈10 nm) CdS buffer layer. The decreased thickness of the buffer layer can reduce the parasitic absorption loss of the solar cell. As the result, the short‐circuit current density of the solar cell is increased. On the other hand, the Mn2+ in the deposition solution can diffuse into the CZTSSe layer during the deposition of the buffer layer. The incorporation of Mn in CZTSSe would decrease the acceptor level of CZTSSe, reduce the defects at the CZTSSe/CdS interface, and increase the activation energy for the main recombination path in CZTSSe solar cell. These can lead to the reduction of the carrier recombination in the depletion region of the solar cell. As the result, the open‐circuit voltage of CZTSSe solar cell is improved. By using the ultrathin CdS buffer layers, the efficiency of CZTSSe solar cell is improved from 10.0% to 12.0% (active area efficiency).