Analysis of the Voltage Losses in CZTSSe Solar Cells of Varying Sn Content.

ABSTRACT: The performance of kesterite (Cu₂ZnSn(S,Se)₄, CZTSSe) solar cells is hindered by low open circuit voltage ( V_oc). The commonly used metric for V_oc-deficit, namely, the difference between the absorber band gap and qV_oc, is not well-defined for compositionally complex absorbers like kesterite where the bandgap is hard to determine. Here, nonradiative voltage losses are analyzed by measuring the radiative limit of V_oc, using external quantum efficiency (EQE) and electroluminescence (EL) spectra, without relying on precise knowledge of the bandgap. The method is applied to a series of Cu₂ZnSn(S,Se)₄ devices with Sn content variation from 27.6 to 32.9 at. % and a corresponding V_oc range from 423 to 465 mV. Surprisingly, the lowest nonradiative loss, and hence the highest external luminescence efficiency (QE_LED), were obtained for the device with the lowest V_oc. The trend is assigned to better interface quality between absorber and CdS buffer layer at lower Sn content.

SUBMITTER: Azzouzi M 

PROVIDER: S-EPMC6558638 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature