Defects in Cu2ZnSn(S,Se)4 solar cells studied by photoluminescence, admittance and IVT

Cu
₂
ZnSn(S,Se)
₄
thin film devices fabricated with a new, fast and environmental friendly preparation method are investigated by defect spectroscopy and transport measurements. Defect levels in sulfide-based as well as sulfur-selenide based kesterite devices are studied using admittance, temperature-dependent current-voltage analysis and photoluminescence. We find that the series resistance of the devices is activated with an energy of 80-100meV while the defect activation energies from admittance analysis shows activation energies of 200meV and 260meV for sulfur-based and Cu
₂
ZnSn(S
_0.6
Se
_0.4
)
₄
devices, respectively. These admittance derived energies are consistent with the photoluminescence transition at a room temperature. The photoluminescence quenching activation energies of 130-140meV were determined for both devices and attributed to donor level of the quasi donor acceptor pair transition observed at low temperature.