 The researchers developed a new method for fabricating perovskite solar cells, PSCs, using a thermally-polymized additive as the polymer template. This additive forms monolithic perovskite grains and a unique mortise 10 and structure, which reduces non-radiative recombination and improves the balance between the interface charge extraction and the charge transport. As a result, the PSCs achieved a certified efficiency of 24.55% and maintained more than 95% initial efficiency after 1100 hours of testing under the ISOS-L2 protocol and more than 80% initial efficiency after 1000 hours of testing under the ISOS-D3 accelerated aging test. This article was authored by Fang Fang Wang, Moobai Li, Zhou Shuangjian, and others.