Ultrafast Single‐Band Upconversion Luminescence in a Liquid‐Quenched Amorphous Matrix

Abstract Achieving single‐band upconversion is a challenging but rewarding approach to attain optimal performance in diverse applications, such as multiplexed molecular imaging, security coding, and nonlinear photonic devices. Here, highly efficient single‐band upconversion luminescence in the green spectral regime (16.4 times increase in emission at 525 nm) accomplished by realizing minimal energy loss from two‐photon upconversion in a newly synthesized liquid‐quenched amorphous matrix is reported. In contrast to previously reported single‐band upconversion, this phenomenon originates from the elevated transition probability of the host sensitive transition via changes in the host matrix's microstructure. The elevated transition probability facilitates ultrafast decay of upconversion luminescence with decay times as short as 0.2 µs, the fastest decay ever reported. The material in this study therefore has strong potential for use in photonic devices demanding high upconversion efficiency with a fast response time, which to date has been inaccessible using upconversion materials.