CuInGaSe2 thin-film solar cells with 11.5% efficiency: An effective and low-cost way of Na-incorporation for grain-growth

Cu(In,Ga)Se 2 (CIGSe) based solar cells have received considerable interests because they have reached the commercialization stage. High efficiency CIGSe based solar cells are often fabricated via post deposition treatment (PDT) with alkali metal element incorporation. In this work, we present an effective and low-cost way of Na-incorporation for photoelectric conversion efficiencies (PCE) promotion of CIGSe solar cells. Soda-lime glass (SLG) was used as both substrate and cover during the PDT procedure for Na doping. The effects of different substrate and cover on the grain size and phase composition of CIGSe films were studied in detail. The Na- incorporation from SLG significantly improved the grain growth, charge carrier density and V oc of CIGSe solar cells. At last, a best 11.53% PCE CIGSe solar cell was achieved at optimal condition.