Design rules for key factors governing two-dimensional MXenes to programmable interfacial engineering

초록

This review evaluates the key factors influencing the performance of MXenes (M n+1 X n T x ) in photovoltaic applications. It systematically connects etching chemistry, compositional choices, surface terminations, flake morphology, defect engineering, and doping strategies with device performance. We propose a factor-based framework that goes beyond mere descriptive categorization to enable prescriptive design, facilitating role-specific optimization of MXenes as electron transport layers, hole transport layers, interfacial modifiers, electrodes, and absorber additives. Titanium carbide MXenes, particularly Ti 3 C 2 T x , have achieved record efficiencies in perovskite solar cells, surpassing 26.78%. This success is attributed to work function tuning, defect passivation, and improved charge extraction. Although nitride MXenes possess theoretically superior conductivity, they encounter significant synthesis and oxidation challenges. We outline specific strategies, such as low-temperature ammoniation and molten-salt etching, to address these issues. We differentiate between lattice vacancies, which limit transport and affect the fill factor (FF), and surface or edge defects, which regulate recombination and influence open-circuit voltage (V OC ) and hysteresis. A unified framework that connects process, structure, and performance, along with a decision flowchart, aids in the rational selection of materials based on their intended role in the device and the primary bottlenecks.

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