Role of deep levels and interface states in the capacitance characteristics of all-sputtered CuInSe2/CdS solar cell heterojunctions

All-sputtered CuInSe2/CdS solar cell heterojunctions have been analyzed by means of capacitance-frequency (C-F) and capacitance-bias voltage (C-V) measurements. Depending on the CuInSe2 layer composition, two kinds of heterojunctions were analyzed: type 1 heterojunctions (based on stoichiometric or slightly In-rich CuInSe2 layers) and type 2 heterojunctions (based on Cu-rich CuInSe2 layers). In type 1 heterojunctions, a 80-meV donor level has been found. Densities of interface states in the range 1010–1011 cm2 eV−1 (type 1) and in the range 1012–1013 cm−2 eV−1 (type 2) have been deduced. On the other hand, doping concentrations of 1.6×1016 cm−3 for stoichiometric CuInSe2 (type 1 heterojunction) and 8×1017 cm−3 for the CdS (type 2 heterojunction) have been deduced from C-V measurements.