Mxene regulates the stress of perovskite and improves interface contact for high-efficiency carbon-based all-inorganic solar cells

Poor interfacial contact and residual stress in perovskite solar cells (PSC) are known to reduce device stability and photoelectric performance. Herein, a novel strategy was developed by embedding TiO2 NPs into CH3COO− (AC−)-functionalized MXene (MX, Ti3C2) as an electron transport layer (ETL). The strong interaction between the AC− of MX and Pb2+ of perovskite reinforces the interfacial contact between the ETL and perovskite layer, releasing harmful lattice strain. Meanwhile, charge accumulation and non-radiative carrier recombination at the interface were effectively suppressed. As a result, the carbon-based CsPbI2Br PSC achieved a champion efficiency of 15.48 %, and the large-area (≥1 cm2) device also demonstrated high efficiency (13.06 %). The CsPbIBr2 and CsPbI3 counterparts yielded high efficiencies of 11.22 % and 14.59 %, respectively. Moreover, the devices showed excellent environmental stability, maintaining 91 % of original efficiency after being stored in air at a relative humidity of about 20–30 % for 1250 h. It also retained 85 % of its original efficiency when stored at 85 °C in a nitrogen atmosphere for > 400 h.