Effect of Cesium for Cu(In,Ga)(S,Se)$_{2}$ Solar Cells Using Photothermal Atomic Force Microscopy Under Various Photoexcitation Conditions

We have performed photothermal (PT) measurements by atomic force microscopy, by which nonradiative recombination of photoexcited carriers can be examined very locally, on Cu(In,Ga)(S,Se)
$_{2}$
(CIGSSe) materials in order to investigate CsF-treatment effects. From the PT signal images taken under various photoexcitation conditions and by comparing those images taken on CIGSSe samples with or without the CsF-treatment, we have found the possibility that the nonradiative recombination centers, which should exist along grain boundaries and may be distributed at a CdS/CIGSSe interface, are well passivated by the CsF-treatment.