Quantitative incorporation of sodium in CuInSe/sub 2/ and Cu(In,Ga)Se/sub 2/ photovoltaic devices

Sodium was deliberately introduced into CuInSe/sub 2/ and Cu(In,Ga)Se/sub 2/ photovoltaic solar cells in a controlled manner. The amount of sodium added was varied in order to pinpoint the range of sodium concentrations in the CuIn(Ga)Se/sub 2/ film for optimal performance. Films were analyzed using secondary ion mass spectroscopy and induced-coupling plasma spectroscopy to quantify the sodium concentration. The results are compared with the calculation. Finished devices show improvements in open-circuit voltage, fill factor and hole density for sodium concentrations in the range of approximately 0.05 to 0.5 atomic percent.