Effect of oxidation-reduction heat treatments on CuInSe2/CdS device behavior [solar cells]

All changes in the spectral responses and current-voltage characteristics of CuInSe₂/CdS solar cell devices due to oxidation (air)-reduction (H₂) heat treatments can be explained by the changes in CuInSe₂ resistivity. An investigation of the effect of reducing heat treatments is presented. Spectral response and temperature-dependent current-voltage (J- V vs. T) measurements were carried out as a function of oxidation-reduction heat treatments. The device was heat treated in air or H₂ at 200°C in order to achieve oxidized or reduced states, respectively. As observed previously, spectral response and J-V characteristics of the CuInSe₂/CdS heterojunction solar cell were completely reversible during the oxidation-reduction cycle. These measurements allow the various regions of the operating CuInSe₂/CdS heterojunction solar cell to be probed. Spectral response and barrier height measurements (V _oc vs. T) provide information about the main heterojunction, while the low-temperature forward bias J-V vs. T characteristics can be analyzed to obtain the parameters of the back diode Mo/CuInSe₂ contact as the device is cycled through oxidized and reduced states