Plasmons Enable Ultralow Threshold Solid-State Triplet Fusion Upconversion with a 2D Sensitizer

transfer process is identified as a key factor for the device performance. This work demonstrates that plasmon excitation overcomes the low far-field absorption of 2D transition-metal dichalcogenide (TMD) sensitizers. Consequently, monolayer TMDs can achieve solid-state upconversion with a performance among the best reported.