  A contactless effective series resistance imaging method for large area
perovskite solar cells that is based on photoluminescence imaging with
non-uniform illumination is introduced and demonstrated experimentally. The
proposed technique is applicable to partially and fully processed perovskite
solar cells if laterally conductive layers are present. The capability of the
proposed contactless method to detect features with high effective series
resistance is validated by comparison with various contacted mode luminescence
imaging techniques. The method can reliably provide information regarding the
severeness of the detected series resistance through photo-excitation pattern
manipulation. Application of the method to sub-cells in monolithic tandem
devices, without the need for electrical contacting the terminals, appears
feasible.
