Benzodithiophene derivative 2D spacer as a defect passivation material in metal halide perovskite solar cells

Defect passivation is an efcient strategy for improving the performance of perovskite solar cells (PSCs). In this study, we introduced a benzodithiophene-based 2D spacer with a short alkyl chain (BDT-C2) into a perovskite flm for defect passivation. The introduction of BDT-C2 did not exhibit the 2D perovskite structure, but an optimized amount (0.01 wt%) induced vertically oriented (110) planes of perovskite flm. However, when excess BDT-C2 was added to the perovskite flm, the orientation collapsed. The nanostructure of the flm was correlated with the device performance. The (110) plane was mostly arranged in the vertical orientation, and the device performance was best under the optimal conditions. Despite the enhancement of the device performance, the grain size of the perovskite was almost unaltered with the addition of BDT-C2. By measuring the light intensity-dependent Voc and Jsc, we confrmed that there was reduced charge recombination owing to defect passivation under the optimal conditions.