A chlorophyll derivative, sodium copper chlorophyllin (NaCu-Chl), is utilized to passivate the defects at the perovskite film surface via a solution post-treatment method. It is found that NaCu-Chl not only suppresses the defect-induced nonradiative recombination but also improves the film morphology. Moreover, NaCu-Chl treatment also facilitates efficient hole extraction from perovskite to Spiro-OMeTAD. As a result, NaCu-Chl-treated MAPbI₃ PSCs produce an optimal power conversion efficiency (PCE) of 20.27% with better ambient and thermal stability. This work offers an insight into the application of natural products and derivatives for fabrication of PSCs.