The incorporation of Na into Cu(Inl-xGax)Se2 thin-films is known to lead to an improvement in device performance. The authors use X-ray photoelectron and Auger electron spectroscopies to determine the chemical nature of Na in Cu(Inl-xGax)Se2 thin-films. The Na concentration is determined to be ∼ 0.1 atomic percent in the bulk of Cu(In1-xGax)Se2 thin-films. The Na is chemically bonded to Se. The authors propose a model invoking the replacement of column III elements by Na during the growth of Cu(Inl-xGax)Se2 thin-films. These Nain and NaGa defects act as acceptor states to increase the p-type conductivity of Cu(In1-xGax)Se2 thin-films.