Semiconductor nanocrystals‐based triplet‐triplet annihilation photon‐upconversion: Mechanism, materials and applications

Triplet‐triplet annihilation photon upconversion (TTA‐UC) has emerged as a promising strategy for enhancing solar energy harvesting efficiency by converting two low‐energy, long‐wavelength photons into a high‐energy, short‐wavelength photon. In recent years, semiconductor nanocrystals have gained significant attention as efficient photosensitizers for TTA‐UC due to their excellent triplet energy transfer efficiency and the ability to tune their bandgap across the solar spectrum. This review focuses on the mechanism of NC‐based TTA‐UC, emphasizing key parameters to evaluate the performance of TTA‐UC systems. The influence of various material‐related factors on the overall NC‐based TTA‐UC performance is thoroughly discussed. Moreover, recent advances in solid‐state approaches for NC‐based TTA‐UC are highlighted, along with an overview of the current status of applications in this field. Lastly, this review identifies the challenges and opportunities that lie ahead in the future development of NC‐based TTA‐UC, providing insights into the potential advancements and directions for further research.