MXene surface termination chemistry and interface engineering for optoelectronics

Surface terminations of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides (MXenes) govern the interplay among metallic conductivity, optical transparency, and tunable work functions, which collectively dictate their optoelectronic interface behavior. While work function tuning and defect passivation are traditionally studied in isolation, they are underlying manifestations of the same chemical variable that governs charge carrier dynamics. Building on this premise, this review discusses termination chemistry as a tunable design parameter that links initial etching conditions to device-level performance via termination-dependent optoelectronic mechanisms. By examining three representative applications—transparent conductive electrodes, perovskite solar cells, and photodetectors—we demonstrate that device performance is intrinsically tied to the termination composition established during synthesis. Specifically, we show how device-specific bottlenecks, such as energy-level alignment or charge recombination, originate from specific surface chemical states. We further suggest that the precise control and reproducibility of the synthesis-to-interface mapping are the critical constraints for transitioning MXene optoelectronics from laboratory-scale demonstrations toward manufacturable technologies. The design logic articulated herein provides a unified framework for advancing MXene-based flexible electronics and perovskite devices, offering broader insights for other 2D systems where surface chemistry dictates performance.