In Cu(In,Ga)Se 2 (CIGS) thin-film solar cells, interface recombination is one of the most important limiting factors with respect to device performance. Herein, metal-insulator-semiconductor samples are used to investigate and compare the passivation effects of Al 2 O 3 and HfO 2 at the interface with CIGS. Capacitance-voltage-frequency measurements allow to qualitatively and quantitatively assess the existence of high negative charge density (Q f % À10 12 cm À2 ) and low interface-trap density (D it % 10 11 cm À2 eV À1 ). At the rear interface of CIGS solar cells, these, respectively, induce field-effect and chemical passivation. A trade-off is highlighted between stronger field-effect for HfO 2 and lower interface-trap density for Al 2 O 3 . This motivates the usage of Al 2 O 3 to induce chemical passivation at the front interface of CIGS solar cells but raises the issue of its processing compatibility with the buffer layer. Therefore, an innovative Al 2 O 3 /HfO 2 multistack design is proposed and investigated for the first time. Effective chemical passivation is similarly demonstrated for this novel design, suggesting potential decrease in recombination rate at the front interface in CIGS solar cells and increased efficiency. 300 C annealing in N 2 environment enable to enhance passivation effectiveness by reducing D it while surface cleaning may reveal useful for alternative CIGS processing methods.