Grain boundaries (GBs) in perovskite solar cells (PSCs) have been found to be detrimental to the device performance. Scientists in Hong Kong developed a unique approach by modifying the perovskite GBs with flakes of high-mobility 2-D materials, which can conduct holes from the GBs to hole transport layers in the PSCs and make the GBs hole channels in the devices. This work presents a cost-effective strategy for improving the performance of PSCs by using high-mobility 2-D materials.