Grain Boundary Engineering of Halide Perovskite CH₃NH₃PbI₃ Solar Cells with Photochemically Active Additives

In this study, we investigate the nanoscale effects of photochemically active additives of benzoquinone (BQ), hydroquinone (HQ), and tetracyanoquinodimethane (TCNQ) on grain boundaries in CH 3 NH 3 PbI 3 solar cells. We employ scanning probe microscopy under light illumination, in particular Kelvin probe force microscopy, to study surface potential changes under laser light illumination. The recently found improvement in the efficiency of BQ added solar cells can be clearly seen in vanishing contact potential differences at grain boundaries under illumination, rendering the material more uniform under solar cell operating conditions. These effects are observed for BQ, but not for HQ and TCNQ. Our findings shed light onto halide perovskite materials and the functional additive design for improved solar cell performance.