Cation exchange enabled improved perovskite infiltration in triple-mesoscopic carbon perovskite solar cells

Poor infiltration of perovskite precursor into the mesoscopic stack is the major cause of comparatively inferior device performance in the triple-mesoscopic architecture of carbon-based perovskite solar cells (C–PSCs). In this study, we employed the cation exchange method to improve perovskite solution infiltration. 2D (PEA)2PbI4 perovskite is infiltrated into the triple mesoscopic architecture, and then it is converted to 3D FAPbI3 and FAxMA(1-x)PbIyBr(3-y) perovskite via cation exchange. The rapid infiltration of the (PEA)2PbI4 perovskite precursor into the mesoporous scaffold resulted in increased pore filling and better infiltration of the converted 3D perovskite. This was validated using optical microscopy, SEM with EDX mapping, and photoluminescence imaging. The conversion of 2D (PEA)2PbI4 into 3D FAPbI3 and FAxMA(1-x)PbIyBr(3-y) perovskite was confirmed using XRD and UV–Vis spectroscopy. This technique produces devices with higher performance and reproducibility compared with conventional one-step infiltrated devices. The device with cation exchange-assisted infiltration of FAxMA(1-x)PbIyBr(3-y) shows 12.10% PCE and excellent long-term stability, with unencapsulated devices retaining around 65% of initial performance after 1000 h.