Characterization of CZTS monograin membrane cells with low-intensity and wavelength-selective light soaking

Measurements of the photovoltaic (PV) activity of solar cells under low-light conditions and different wavelength-selective filters can supply useful information about the nature, the location and the activation of defects, and recombination mechanisms inside the heterojunction and its interfaces. In this work we use this approach for the characterization of crystalsol monograin membrane kesterite (CZTSSe) solar cells. The time dependence of the open circuit voltage, short circuit current, fill factor and conversion efficiency, under low intensity of white, red, green and blue light is studied and related to carrier recombination processes in the bulk of the absorber and its interfaces with the CdS buffer and the electrodes. The low-light behavior of the cells is discussed in relation to their PV performance under standard test conditions (1000 W/m2) and their external quantum efficiency. Reversible and irreversible contributions to the light-soaking effects are further analyzed. Finally, photoluminescence and electroluminescence imaging was used to elucidate the spatial homogeneity and quality of the monograin cells.