Alex Sergey Ionkin

A simple solution-based route to high-efficiency CZTSSe thin-film solar cells

Solution-based Cu2ZnSn(S,Se)4 (CZTSSe) thin film deposition routes focusing on chemistries with attractive scalability and handling characteristics, while delivering high efficiency devices are promising technologies for low-cost solar cells. In this paper we describe a new approach for the fabrication of CZTSSe thin films using inks comprised of mixtures of binary and ternary metal-chalcogenide nanocrystals dispersed in simple organic solvents. The resulting blended inks can be coated under ambient conditions to give precursor films which are in turn converted to device-quality CZTSSe absorbers via thermal annealing in a selenium atmosphere. Using this approach we have demonstrated CZTSSe solar cells with total area efficiencies in excess of 8.5% (or 9.6% per active area) under 1 Sun AM1.5 illumination.

Characterization and understanding of performance losses in a highly efficient solution-processed CZTSSe thin-film solar cell

We present results on the characterization of a highly efficient CZTSSe solar cell fabricated using a solution-based process, aiming to gain a better understanding of its efficiency-limiting causes. Under red light illumination, we observed a red-kink in the current-density versus voltage (J-V) curve, likely due to a persistent photoconductivity in the buffer layer. Temperature-dependent J-V analysis suggests that interface recombination is the dominant loss mechanism. Defect analysis using admittance spectroscopy (AS) shows a single bulk defect level at ~63 meV and may be attributed to copper vacancy (VCu). The carrier concentration of the device determined using drive-level capacitance profiling (DLCP) is ~2.5×1016 cm-3.