Performance and stability enhancement of Cu(InGa)Se2 solar cells on ultrathin glass by potassium incorporation

Abstract Flexible Cu(InGa)Se2 solar cells fabricated on metal foils and plastics have achieved high conversion efficiency so far. However, metal impurities and low temperature tolerance hinder them from further considerable development. Here, 150 μm-thick ultrathin glass with desirable advantages was applied as substrate for Cu(InGa)Se2 solar cell. Potassium element was doped by a simple method during the post-selenization process. The results showed that the KInSe2 phase existed in K-doped Cu(InGa)Se2 films. The K-doped CIGS films were more compact than the pristine one due to the fact that K incorporated in films could form quasi-liquid alkali-metal-Se compounds and improve the compactness of films. K-incorporated CIGS films exhibited enhanced p-type conductivity and different surface energy level. Consequently, K-doped Cu(InGa)Se2 solar cell achieved an optimal efficiency of 8.3 %, which was relatively 43 % higher than that of pristine solar cell. Investigation of performance and stability of solar cells manifested that the K incorporation retarded the performance degradation of device during cyclic bending.