Photo-dynamics in 2D materials: Processes, tunability and device applications

The past decade has witnessed the rise of low-dimensional materials, such as graphene, transition metal dichalcogenides, black phosphorus, organic–inorganic hybrid perovskites and MXenes. They have received tremendous attention due to their peculiar properties, as compared to their bulk phase. These unique properties have ushered in a paradigm shift in many applied fields and technologies including, but not limited to optoelectronics, catalysis, biomedical research and quantum information sciences. The fundamental processes determining the performance of devices, utilizing the low-dimensional materials, are photogeneration of charge carriers and carrier transport. A detailed understanding of these processes is therefore indispensable to the design and optimization of advanced high-performance low-dimensional materials-based devices for broadband photodetection, high-speed modulation, high-efficiency solar energy harvesting, and energy storage, among others. Herein, we critically review recent advances in studies of photoinduced carrier dynamics in low-dimensional semiconductors and semimetals. Transient carrier generation, trapping and recombination dynamics can be controlled by temperature, charge transfer in hybrid structures, electrical and magnetic field, and stress. Revealing the mechanisms and strategies of their tuning should help design and optimize multifunctional materials to enable high-performance devices. In this review, we do not focus exclusively on the photoinduced species (excitons and charge carriers), but also discuss possible strategies to adjust their properties and their impact on device characteristics. To conclude, we summarize current status, describe existing challenges, and provide a subjective opinion on future opportunities to advance this exciting field. We hope that this review will be appealing to a broad materials physics audience and will be helpful in exploring new physics and discovering theory guided novel materials with robust performance.