Interfacial Engineering of Au@Nb 2 CT x -MXene Modulates the Growth Strain, Suppresses the Auger Recombination, and Enables an Open-Circuit Voltage of over 1.2 V in Perovskite Solar Cells.

Defects at the interface of charge transport layers can cause severe charge accumulation and poor charge transferability, which greatly affect the efficiency and stability of stannic oxide (SnO 2 )-based perovskite solar cells (PSCs). Herein, a new type of MXene (Nb 2 CT x -MXene) is applied to the interface of SnO 2 layers to passivate the interfacial defects and promote charge transport. Nb 2 CT x -MXene in PSCs realizes the role of boosting the conductivity, reducing the tin vacancies in the interstitial void of the SnO 2 layer, decreasing the defect density, and aligning the bandgap. Afterward, Nb 2 CT x -MXene is decorated with gold nanospheres, which has the ability to modulate the tensile strain of perovskites and suppress the Auger recombination. Eventually, the Au@Nb 2 CT x -MXene-modified device yields an excellent power conversion efficiency (PCE) of 23.78% with a relatively high open-circuit voltage of 1.215 V ( E g ∼ 1.60 eV). The unencapsulated devices maintain 90% of their initial PCE values after storage in the air with a relative humidity of 40% for 1000 h and remain above 80% of their initial efficiency after operation at the maximum power point for 500 h under 1 sun illumination. Our work provides an avenue to fabricate high-efficiency and stable PSCs with MXene adapting to commercial development.