Imaging defect passivation in grain interiors and grain boundaries of RbF(S)-treated Cu(In,Ga)Se <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg" display="inline" id="d1e331"> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mn>2</mml:

RbF post-deposition treatments provide an effective way to increase the performances of Cu(In,Ga)Se 2 (CIGSe) solar cells, but the role of heavy alkali elements at the microscopic scale is still unclear. Here, we investigate the impact of an RbF post-deposition treatment under S atmosphere. An increase of the conversion efficiency from 12.4% to 16.3% is enabled by a better collection of charge carriers and a 100 mV increase in V oc . Using high-resolution hyperspectral cathodoluminescence mapping, we show that the RbF(S) treatment passivates low-energy defects attributed to copper vacancies, effectively resulting in an efficient reduction of non-radiative recombination at grain boundaries and in grain interiors. • Cathodoluminescence images reveals the distribution of defects at the nanoscale. • An RbF post-deposition treatment under S atmosphere is applied to Cu(In,Ga)Se2. • Passivation effects are evidenced at grain boundaries and in grain interiors. • The efficiency of RbF(S)-treated CIGSe solar cells is increased from 12.4% to 16.3%.