Polymerization stabilized black-phase FAPbI3 perovskite solar cells retain 100% of initial efficiency over 100 days

The black perovskite ( α -FAPbI 3 ) tends to spontaneously transform into the yellow non -perovskite ( δ -FAPbI 3 ) under ambient conditions, which degrades the performance and stability of FAPbI 3 -based perovskite solar cells (PSCs). Herein, we applied an in-situ polymerization controlled growth (IPCG) strategy for crystal grain to suppress the α-to-δ phase conversion. Polymerization of 2-(Dimethylamino) ethyl methacrylate (DMAEMA) contained in the antisolvent created polymers (denoted as Poly(D)) which acted to simultaneously increase the perovskite grain size, passivate defects, stabilize the black phase, and block moisture penetration, thus greatly improving photovoltaic performance and stability. The resulting FAPbI 3 -based PSC (FTO/SnO 2 /Perovskite/Spiro-OMeTAD/Au) delivered a high power conversion efficiency (PCE) of ~ 21% (cf. ~ 16.0% PCE for the pristine FAPbI 3 device). Further, the polymerization strategy delivers PSCs with remarkable stability, with 100% of the initial PCE performance being retained over 104 days under ambient conditions (room temperature, RH = 50 ± 5%) without encapsulation of the device.