Defect levels in CdS/CuInSe2 thin-film solar cells

Thermally stimulated capacitance spectroscopy has been employed to study the defect levels in high-efficiency, CdS/CuInSe2 thin-film solar cells. Voltage bias changes were used to probe the majority-carrier traps and light bias was employed, for the first time, to reveal minority-carrier traps. The light bias thermally stimulated capacitance has shown the presence of a distribution of electron trapping levels in CuInSe2. The capacitance under steady illumination shows that the traps produce a large photocapacitance. The implications of these observations in terms of device performance is discussed.